I actually almost never sign onto IM any more, so it's a moot point for me. I used to block people who annoyed me, but now I only allow my name to show up in chat for particular people. So I guess I block everyone, except for my closest friends and colleagues?

It's probably a metaphor for how I think about friendship these days. I'm a lot more careful with my time.

Whom do you block on IM/Gchat?