The famed technology writer Steven Levy starts his long-form history of Facebook's newest product—Graph Search—by describing it as a feature that "promises to transform its user experience, threaten its competitors, and torment privacy activists." Though it takes quite a lot to torment us these days, Graph Search does raise a few eyebrows.

The new feature allows users to use structured searches to more thoroughly filter through friends, friends of friends, and the general public. Now one can more easily search for "My friends who like Downton Abbey" or "People in San Francisco, California who work at Facebook." Facebook then returns a list of individuals whose public or shared aspects of their profile match the search terms.

Now there's nothing inherently wrong with being able to look at information that is either public or has been chosen to be shared. Yet this new search allows strangers to discover information about you that you may not have intended them to find.

There's a difference between putting information out there for anyone to find and putting information out there to be searched and sorted. If you walk down a crowded public street, you are probably seen by dozens of people—but it would still feel creepy for anyone to be able to look up a list of every road you've walked down. This is why Google Street View, for example, disguises the identity of people photographed on public streets, even though the information was not private or secret.

Another notorious example of this was when a group of Fordham Law students put together a dossier of publicly available information about Supreme Court Justice Antonin Scalia. Though individual pieces of information may be available, when they are brought together through a search or a compilation, that's when the privacy goose bumps come out.

Facebook's Graph Search presents the problem of discoverability. One can have a good balance of privacy and openness if information is available, but not easily discoverable. You might not mind if people specifically interested in you look at your Likes, but you may not want to have a market researcher pull the list and add it to an ad targeting profile. You might be okay if a new person you met at a conference looks you up on Facebook, but you may not want a creepy guy searching through Facebook's loose networks to find someone to stalk. All of a sudden, what people once thought was shared only to their Facebook audience—whether friends, friends of friends, or member of the public with a specific reason to look you up—is now readily available via Graph Search. This feature has rolled everyone, by default, into a dating service ("Single females in San Francisco who like Radiohead") and a marketing database ("People under 25 who like Coca-Cola").

Naturally, many people are uneasy with this new feature. This is par for the course when it comes to big Facebook changes. As Timeline rolled out, people were shocked by sudden accessibility to old wall posts, which were posted at a time when private Facebook messages did not exist. People used Facebook very differently four years ago than they did four months ago, and that realization manifest itself in the appearance of embarrassingly personal communications. Norms change as technologies go through iterations, yet these iterations raise trouble when one era's expected levels of privacy are now exposed to new methods of discoverability.

To illustrates the problem with outdated information, for example, someone may not remember that she "liked" the "Samsung Mobile" page back in college, even if she was okay with that being public information at the time. But now the fact that she shows up in "People who work at Apple, Inc. who like Samsung Mobile" could lead to a heavy dose of awkward. (Forbes' Kashmir Hill tests this out on a number of Facebook employees, including Mark Zuckerberg.)

As Facebook's Graph Search gets rolled out, it may be a wakeup call for people to examine—and rein in—their privacy setting. On Facebook, things are more available by default than people may think. But even beyond specifically public settings, actions and photos that were once lost in the sands of Timeline are now more easily discoverable by strangers with loose ties, forcing us to reassess what we actually think is private and what is not.

Next, we'll show you how to adjust your privacy settings so you can better control what shows up in Graph Search results.