When Yahoo bought Tumblr, it suggested that its adult and porn blogs would be left alone.

Users found out this wasn't true when a new adult blog search policy went public on Thursday, capping Tumblr's quarantine on adult content, which now also includes excluding adult blogs from Google, Bing, Yahoo, and other search engines.

UPDATE Sunday, July 21: Read After backlash, Yahoo's Tumblr quietly restores adult, NSFW blogs

The changes render an estimated 10% of Tumblr's userbase invisible and unfindable.

Now, around 12 million Tumblr blogs marked "adult" have been removed from Tumblr's internal search; this follows the revelation two months ago that adult blogs were no longer indexed by Google, and the pre-sale removal of Tumblr's "Erotica" category from its category index.

Tumblr's "Erotica" category had been launched in January 2010 with much sex-positive fanfare - it would appear that the days of Tumblr's tolerance are long gone.

The change to its content restrictions came two months after press heard Yahoo CEO Marissa Mayer say in May that Tumblrs which aren't "brand safe" - alluding to porn and adult blogs - would be left alone.

Removal from search in every way possible is the closest thing Tumblr could do to deleting the blogs altogether, without actually removing 10% of its user base.

Under Tumblr’s new rules, adult-rated blogs and their posts will no longer show up in tags, period. Tags are the way blogs are searched, and found, on Tumblr.

The only way to find a post from a blog marked adult - or to find and discover adult blogs - is to receive the link directly, such as if another user reblogs a post, you are already following the blog, or you are sent a direct link.

Blogs removed from both Tumblr and Google, Bing, Yahoo! Search

To say that Tumblr users are angry would be the understatement of the year.

The removal from internal search cuts off the adult blog user from the rest of the Tumblr community; since Tumblr has enabled robots.txt and inserted the rule (Disallow: /) that tells search engines not to search pages on all Tumblr adult blogs, the adult blog user is now cut off from Google search as well.

In fact, that rule prohibits all standards-compliant search engines from indexing the blogs, a list that includes Google, Ask, AOL, Baidu, Bing and Yahoo.

Longtime sex blogger "Bacchus" of Eros Blog - who is not a Tumblr user - discovered two months ago that Tumblr had quietly made it so all blogs marked as "adult" are now omitted from Google search, cut off from the rest of the Internet.

Tumblr users were not made aware of the fact that adult blogs are not indexed by Google no matter what preference the user has expressed.

He wrote (link NSFW),

I’ve discovered that Tumblr uses robots.txt to bar all search engine access to blogs flagged as adult. If you’ve got an adult Tumblr, go look at your own settings. Do you see that first checkbox, the one that says “allow search engines to index your blog”? It’s nicely checked, it’s not greyed out, but if your blog is flagged “adult” it’s a lie. To answer the question “What happens to blogs that are flagged NSFW or Adult?” Tumblr offers this handy chart. The key piece of information is the white space indicated by my red superimposed arrow: That’s right - where the “Blog indexed by Google” row intersects the “Adult Blogs” column, we find a ringing silence.

This means if a user runs a blog marked "adult" wants to publicize a fundraiser, get the word out about life changes, post about sex ed with non-illustrated images, share a favorite brownie recipe, or share news about their experiences at a protest, these posts will not show up on either Tumblr's search engine or Google.

Of course, Tumblr is able to flag a user's account as adult regardless of the user's consent.

This news all comes on the same day that Tumblr's iOS update for Apple rolled out changes that remove search results for #gay, #lesbian and #bisexual (though leave #bi, #lgbt and #queer intact).

This appears to be in conforming with Apple's anti-adult policy, though the unfairness of the characterization and effect on Tumblr's community is making its LGBT users see even more red.

There were already ways to block porn on Tumblr if users don’t want to see it, such as Tumblr's Safe Search and Tumblr Savior. The complete elimination from all forms of search is absolutely overkill.

Tumblr doesn't seem to care and this flies in the face of what Tumblr CEO David Karp told The Colbert Report Wednesday night.

As reported in The Tumblr Porn Crackdown Is Here (The Atlantic), Karp told Stephen Colbert:

We've taken a pretty hard line on freedom of speech, supporting our users, creation, whatever that looks like, it's just not something we want to police. When you have somebody like Terry Richardson, or any number of talented photographers, posting tasteful photography, I don't want to have to go in there and draw the line between this photo and this behind the scenes photo of Lady Gaga and her, uh, her nip.

Now Karp just looks like an idiot, and Yahoo looks like it's completely untrustworthy.

So basically, Facebook is having a good week.

Let's just hope that Yahoo's new Tumblr isn't as free and easy with slapping on "adult" content flags as Yahoo's Flickr.

UPDATE: At approximately 9am PST Friday July 19, Tumblr's rep emailed me with a statement. Because it is the exact same statement (copy/pasted into its email to me) that Tumblr sent to The Daily Dot - seen in its article Tumblr Doesn't Care How You Feel About Its Porn Crusade - it answers questions specific to Daily Dot's article, and not this article. It does not make sense to reproduce Tumblr's statement here.

UPDATE: Friday July 19, 6:30pm - Tumblr staff have put up this post, which addresses a glitch - and a fix - with its search for NSFW blogs. The post also explains that the tag blocking around terms #gay, #lesbian and #bisexual have to do with blocking porn, a categorization that is angering LGBT people. Tumblr does not say why it started doing this.

Tumblr's post mentions "adult" blogs in the opening sentence, but does not go on to address the actual issue: the de-indexing of "adult" blogs, the issue with robots.txt, the removal of its "Erotica" category or the issue of walling off a significant population of its users based on content - a change from Tumblr's pre-sale sex-positive ways (such as when it launched the Erotica category in 2010).

Tumblr only mentions "NSFW" blogs, a category that is treated differently.

The post addresses 'concerns about Tumblr censoring' content, but the issue is not censorship. The issue is de-indexing.