I think even that depends a lot of topic and format. I don't mind a technical discussion group at all. A social group on the other hand makes me want to just shut down. At parties I'll often just sit down somewhere and sit there all evening (unless I'm at a club - I like dancing and happily use that as an excuse for not talking), and don't mind talking if someone talks to me, but I won't seek out conversations unless it's a group of geeks talking about subjects I care about.