In what may very well be the most unsurprising news of 2013, Yahoo! (Nasdaq: YHOO) had modified Tumblr.

Here's a statement from Yahoo! from the press release issued in May that it acquired Tunblr: Per the agreement and our promise not to screw it up, Tumblr will be independently operated as a separate business. David Karp will remain CEO. The product, service and brand will continue to be defined and developed separately with the same Tumblr irreverence, wit, and commitment to empower creators.

However, sources today point out that a new adult search policy went into effect Thursday which capped adult blogs. Those include existing ones from Google, Bing, and other search engines.

While it might seem trivial, thre can be two points made:

1. Yahoo! said it wouldn't change Tumblr. It has.

2. The change renders about 10 percent of Tumblr's userbase unfindable and invisible. Though the blogs aren't removed, taking them off of search is basically doing the same thing. That's 12 million blogs which have vanished.

To read the new rules, which are narked not safe for work (NSFW), click here. The link is, actually, safe for work, but highlights the recent changes.

Yahoo! is down 1.8 percent Friday afternoon.