No official blog post from them yet, but Tumblr added Twitter to its friend-finding tool.
Tumblr + Twitter are my favorite social sites. Despite the differences Tumblr (the company) tends to highlight between the two, I think they have a lot in common. Especially in regards to how friendly both networks are about people using them in creative ways, not just as “real person” social objects (as with Facebook and Google+).
And yeah, they added Facebook friend-finding, too. But that’s way less interesting to me, and I’m guessing to most tumblr users :D.