Tumblr has quietly stopped indexing adult-oriented blogs in search engines and in Tumblr's internal searches, a move that has raised new questions about whether the popular blogging service will crack down on porn in the wake of its acquisition by Yahoo. An FAQ doc for adult-oriented blogs, apparently published in the past couple of months, distinguishes between blogs that have occasional adult content and those that publish it regularly. The former continue to be indexed in search engines; the latter are not.

Valleywag, which reported on the changes today, accused Tumblr of beginning to push porn into "an internet sex ghetto." But it's unclear how broadly the updated policy is being applied. Searches for porn Tumblrs on Google and on Tumblr itself continue to yield results by the thousands. And the same social features that help other Tumblrs go viral — following, liking, and reblogging — will continue to surface new porn content on Tumblr even if porn blogs disappear from search engines.

Tumblr did not respond to requests for comment. During an appearance on The Colbert Report last night, CEO David Karp said the company had little interest in trying to remove porn content from Tumblr. "Look, we've taken a pretty hard line on freedom of speech, supporting our users, creation, whatever that looks like, and it's just not something that we want to police," Karp said. For now, it appears, porn blogs on Tumblr are safe — but they may be getting a little harder to find.