Yeah, I've seen that but it's unsatisfactory conversation wise (at least to me), because you can't just jump in (like LJ, where I've found people to be super welcoming if you comment, even if they have no idea who you are). But the pretty probably makes up for it :-)

I do sort of follow a few people's tumblrs for shows I'm watching (it's fun seeing the gifs etc) but the ones I don't know in real life I interact with on LJ still. I should probably sign up just so I can make following them more easy, at the moment I just google.