Google’s search results are undergoing their most radical transformation ever, as a new “Search Plus Your World” format begins rolling out today. It finds both content that’s been shared with you privately along with matches from the public web, all mixed into a single set of listings.

The change is live now, though not everyone will see it until it fully launches over the next few days. It’s only for those signed-in to Google.com and searching in English. You’ll know when it happens, because Google will alert you with a message like this above your search results:

The new system will perhaps make life much easier for some people, allowing them to find both privately shared content from friends and family plus material from across the web through a single search, rather than having to search twice using two different systems.

However, Search Plus Your World may cause some privacy worries, as private content may appear as if it is exposed publicly (it is not). It might also cause concern by making private content more visible to friends and family than those sharing may have initially intended.

The new format and features will also likely cause Google to come under renewed fire that it is leveraging its search engine to favor its own content and crowd out competitors.

Below, a detailed look at what’s involved with Search Plus Your World, from how it works to some of the issues it raises.

Before: Personalized & Social Search Results Separate

Google has had personalized results since June 2005, results from across the web that are given a ranking boost because they are deemed especially of interest to someone, based on their personal behavior and interests. Without the boost, these results might not have made it into the top listings for a particular search.

Personalized results were expanded and presented in a new way in February 2007. Then, in December 2009, you no longer had to opt-in to receive personalized results. They were enabled by default for everyone, to some degree, even if you weren’t signed-in to Google.

Separately, Google has had social search results since October 2009. These are also personalized listings but ones based on the people you know, rather than your personal behavior. They’ve also been given a ranking boost.

Initially segregated from “regular” listings, Google’s social search results were blended into regular results in Feburary 2011 and expanded to include not just content created by those you know but also content shared by them through a variety of social networks.

Now: Personal, Private, Public & Social United

With Search Plus Your World, by default, there’s a new “Personal Results” view that appears. The view personalizes the listings you get based on both your own behavior and social connections, similar to what previously happened. In addition, content that’s been shared with you through the Google+ social network now also appears.

“The social search algorithm, and the personal search algorithm, and the personalized search algorithm are actually one algorithm now, and we are merging it in a way that is very pleasant and useful,” said Amit Singhal, who oversees Google’s ranking algorithms, when I talked with him about the new features.

You’ll know that personalized results are appearing when you see one or both of the indicators below:

The arrow on the left points to a message that, in this example, says that there are “50 personal results and 419,000 other results” that have been found. Some of those 50 results will be blended into the first page of results being shown.

The second arrow highlights a new toggle that Google has introduced, something that many of those who do search engine optimization have wanted for ages. It allows you to switch between personalized and unpersonalized results.

I’ll cover more about the toggle in a bit. When the button with a person icon is shown dark, that means results are being personalized.

Private Content In Your Web Results

To summarize, personalized results include:

Listings from the web

Listings from the web, boosted because of your personal behavior

Listings from the web, boosted because of your social connections

Public Google+ posts, photos or Google Picasa photos (all of which are also listings from the web)

Private or “Limited” Google+ posts, photos or Google Picasa photos shared with you

The last line is the most radical change, that private content will now be visible in what seems to be a search across the entire web. Here’s an example:

In this example provided by Google (complete with its arrow), you can see how one of the photos is showing up with the note: “You shared this – Limited.”

This is a real life example of how personalized search is working for Singhal. He shared this photo of his dog, Chikoo, on Google+ in a limited manner, rather than with the entire world. The other photos of the dog that you can see, including one from his wife, Shilpa, were also privately shared.

Before today’s change, a Google search wouldn’t have found any of these photos when Singhal, his wife or anyone he’s shared them with searched for “chikoo,” which is a fruit. That’s because since the photos were private, Google couldn’t see them.

Instead, if Singhal or others with access to these photos wanted to find them, they would have had to use the completely separate Google+ Search.

The new feature will also work to find Google+ posts that have been shared in a limited manner, or for Google Picasa photos shared privately.

Slightly confusing, you can drill-down into the results to get what Google also calls “Personal Results,” which is a way to get just content from Google+ or Picasa. Remember this from above?

Clicking on the “personal results” link (or “Personal” in the options under “More Search Tools” in the left-column) brings back pure personal results.

No Content From Facebook Or Others, But Google Open To This

I’ve no doubt many people will find it useful to do one search to locate both private and public information at once. However, one of the biggest depositories of private information these days — if not the biggest — is Facebook.

Search Plus Your World doesn’t cover content on Facebook. Or Twitter. Or Flickr. Or any social network or place where content might be shared to a more limited audience. Currently, “Search Plus Your World” would be better described as “Search Plus Google+”

Why are these others missing?

“Facebook and Twitter and other services, basically, their terms of service don’t allow us to crawl them deeply and store things. Google+ is the only [network] that provides such a persistent service,” Singhal told me. “Of course, going forward, if others were willing to change, we’d look at designing things to see how it would work.”

Perhaps Search Plus Your World will prove the carrot or stick that Google’s been after for years to get Facebook to share its data with Google. If the new feature takes off, searchers may wonder why they can’t find privately shared information from their Facebook friends easily on Google.

Then again, Facebook could decide to push back by beefing up its own search features. Currently, Facebook partners with Bing, allowing Bing to personalize its search results for searchers based on what their Facebook friends like.

However, only publicly shared content gets personalized like this. Potentially, Facebook and Bing could work more closely to come up with their own version of Search Plus Your World. That could happen on Bing, or it could happen within Facebook itself.

To date, Facebook’s not spent much time trying to refine its own search results. The primary reason seems to be that the company has repeatedly said that most of the Facebook-based searches it sees are to find people, not to find information about broad topics as happens at Google.

Only You & Those You Share With See Private Content

When Google first showed me Search Plus Your World, a part of me felt unsettled and uncomfortable. As I’ve thought about it more, I think it’s because it feels weird to see “private” content appearing in seems like Google’s “public” search results.

Of course, personalized results aren’t Google’s public results. They are results personalized just for the person viewing them. If private content has been shared with those people, that’s visible. If it hasn’t been, then it’s not.

Google’s also not making it possible to search for anything that you couldn’t already search for before. As I explained, private content shared on Google+ could be found with a Google+ search. Google’s really just making Google+ Search one of its Universal Search sources, in some ways.

In other words, you can search on Google and find matches from Google News, Google Images, Google Video and other Google search services without having to go to them individually. Google+ Search is now another one of those integrated services.

Will It Lead To Concerns?

As said, the ability to search for private content on Google+ isn’t new. However, I wonder if having it integrated into Google’s search results itself might cause some surprises and issues for both Google and its users.

Consider sites selling counterfeit goods. When Google links to these, it gets blamed for promoting counterfeiting, almost as if it created the sites. What’s really happening is that Google comes under fire for giving sites visibility.

Now Google’s going to give greater visibility to private information. Things that people may have forgotten sharing with others will begin to show up serendipitously through ordinary Google searches. Some might not like this, if material they’ve happily forgotten suddenly seems to reappear. Google might take the blame, even though the sharing was done by others.

It might be similar to some of the concerns that came up recently with Facebook Timeline. It’s not that the material Timeline lists wasn’t out there before. But by organizing it, forgotten things are brought back up, as this New York Times article explained well.

Another issue is that it’s very easy with Google+ (as it is with Facebook and Twitter) for someone with access to private content to reshare it publicly. Someone searching on Google, then coming across an unexpected photo or post from a friend, might reshare it to the world.

All this could happen without the search integration. Maybe none of it will be much of an issue at all. But these are concerns that come to mind.

One solution might be an option to exclude your shared content from being searchable. This is something that can be done with public content on the web. You can tell Google or other search engines not to include published material in their search listings. Perhaps Google needs to offer the same for private content, as well (it doesn’t currently).

Secure Search Protects Privacy; Referrers For Advertisers Does Not

Google’s been focused on a bigger concern. Mixing private content in with its search results means that anyone searching without a secure connection potentially exposes that private content to eavesdropping.

And now the full story about why Google rolled out secure search for signed-in users back in October can finally be told. It was necessary preparation to allow for Search Plus Your World to happen today.

“We’ve been working on it for a year, very hard to get it right,” Singhal said, of dealing with the security issues. “It’s just a hard technical problem that we bit off, and it was something that we could not launch until we had it right.”

The encryption that secure search provides means that any private material mixed in with your regular results is protected, seen only by your browser and Google, not by anyone somehow monitoring an internet connection you’re using.

Many publishers were upset about the encryption move last year because, as part of that, Google also stopped providing referrer data, information that shows what searches someone did on Google before visiting a web site.

Expect Google to point to today’s move as a further reason to justify the dropping of referrers. It’s a false justification. Indeed, the move might make things even worse, in terms of privacy, since referrer data is still being passed to advertisers.

Potentially, people are going to search for even more private things than they ever did before. Potentially, they’re going to click on ad links and pass these private search terms to advertisers.

Today’s change does nothing to change my view that Google needs to revisit the referrer blocking and either make it a block for everyone, including advertisers, or find a better way to filter search terms that get made visibile in various ways.

My post from Sunday explains this in more depth: 2011: The Year Google & Bing Took Away From SEOs & Publishers.

Opt-Out, Not Opt-In

Don’t like the idea of personalized search? Disappointingly, Google didn’t go the opt-in route. Instead, you have to deliberately opt-out.

“I think this is a much better experience, at the end of the day,” Singhal said, explaining why the default change was made.

You can opt-out permanently through the Search Settings area on Google. You can also opt-out on a per-search basis using the aforementioned toggle. Click on the globe symbol, and you’ll see unpersonalized results.

This is nice. It’s the first time since December 2009 that people have been able to easily see “normal” results, if they want them.

Personalized Is The New “Normal”

Of course, it’s a mistake to assume that doing this really shows normal results. It will eliminate personalization factors such as your web browsing history (if you provide that to Google through its toolbar in Internet Explorer), your searching history or your social connections.

But geographic targeting — which can be really significant — will still happen. So will targeting by language. Google has begun calling these contextual signals rather than personal ones. Both can be overridden, for those who want. But doing so will still produce results that are still tailored, just to a different geographical location or language.

More important, with Google heading toward 100 million users on Google+, if a good number of those are active users, then they’re logged in to Google. That means the “normal” results they see are personalized. Personalized results are normal; non-personalized are not.

Google Profiles Get Big Push

Another big change as part of today’s release is how people with Google+ accounts are going to be much more heavily highlighted in Google search.

For those logged in, they’ll begin seeing their friends appear right within the search box, like this:

You can see how for Ben Smith, a little picture of him appears next to the search suggestion for his name, which in turn is a link to his Google+ profile, if it were selected.

This is very similar to how Google Direct Connect works for Google+ Business Pages. The results individuals see are biased toward people in their own social networks, similar to how Facebook works when you search for people there.

In other words, if you searched for a friend who had a common name, you should be shown your actual friend’s Google+ profile, rather than someone you don’t know.

In addition, the search results themselves will devote much more room to displaying material from a Google+ person (and actually have been doing so since November):

In the example above, you can see how Ben Smith’s Google+ profile is listed right within the results, with some of his recent posts shown. He’s a friend of Singhal’s, which is why posts with “Limited” sharing appear. The “Friends” circle on Google+ that Singhal has put him in is also shown.

“For me, it’s going to change my relationship on how I look at Google search,” Singhal told me. “It makes it much easier for me to get to what they [someone he knows or is interested in] were saying or if there are web results I should care about.”

What About Promoting Facebook Profiles Or Even Web Sites?

Still, it’s a lot of room devoted to Google+ profiles. While Facebook’s terms have prevented Google from getting some data, I can’t see any particular reason why the type of direct connect suggestion being shown above — as well as the deep display of content from a Facebook profile page — couldn’t also be done for Facebook, not to mention Twitter.

After all, if Google can do expanded sitelinks for social media profiles like at Quora or Twitter, then expanded profile listings showing some relevant posts from those profiles doesn’t seem that difficult.

Of course, it’s harder to do in the case above since the suggestion is made because Smith is known to be one of Singhal’s friends. But Google will be suggesting some celebrities and famous people even if the searcher hasn’t connected to them yet:

The example above shows how photographer Trey Ratcliff is being suggested, with a link to his Google+ profile, even though Singhal isn’t already connected to him.

That helps Ratcliff build his Google+ following. But what if he preferred that his Facebook profile be given a link? Or a link to his own web site? Google used to do this type of thing back in 2008 and 2009:

See how a search for New York Times used to bring up a link directly to the New York Times within the search box? That seems to have quietly disappeared.

Now something similar is turning up, something so tied to only Google+ that you can bet some of Google’s anti-trust critics are going to have a field day saying the company is pushing itself unfairly. And that’s a valid criticism.

People & Pages Suggestions

In fact, if the anti-trust critics need more ammunition, there’s the last component of what’s being rolled out today, suggestions for people and pages on Google+ to follow.

These will appear on the right-hand side of search results, when Google decides they are relevant. Below, what a search for “music” might show:

That’s nice promotion for Google+ (and it also underscores yet again why search marketers simply cannot ignore Google+). But there are still many more people on Twitter and Facebook versus Google Plus.

Google should be able to easily figure out what profiles on other social networks might be relevant to searches. That’s Google’s job as a search engine, if it’s going to make these type of recommendations. But only Google+ gets this type of treatment, and it doesn’t feel right.

Wrapping Up

Overall, I like the integration that allows for searching through private and public material. As I’ve said, I think many people will find it useful.

I do think there are some additional privacy controls that could be added, in particular, the ability for people to opt their content out of being found through search, if they want.

But really, more than anything, I’d like to see Google diligently work in the coming weeks to see how it can level the playing field for the other social networks.

Yes, there are things that Facebook or Twitter might not allow, not without Google cutting deals or agreeing to terms it may not want to. But there are also above-and-beyond things that I think Google probably could do to promote these other services in the way it’s doing for Google Plus. I’d like to see that happen.

More Information

Below, a video from Google about the new features:

Google also has a blog post up with details here. Coverage from other news sources can be found here on Techmeme. Below, about a billion background stories from us that give more context about today’s change.

Postscript: Since the launch, there’s been quite a debate over whether Google is favoring itself in various ways. Please see our follow-up stories below:

Related Stories: Personalized Search

Related Stories: Social Search

Related Stories: Universal Search

Related Stories: Google+

Related Stories: Google+ Profiles, Direct Connect & Suggestions

Related Stories: Privacy

Related Stories: Facebook / Google Data War

Related Stories: Facebook & Bing

Related Stories: Google Anti-Trust

Related Stories: How Search Engines Rank Pages