> Why not an IRC channel?

Yeah, if I wanted to discuss "strong AI" with others, I would probably pick #lesswrong on irc.freenode.net instead of skype or hangouts. And prior to #lesswrong there used to be #sl4, see logs here:

http://diyhpl.us/~bryan/irc/extropians/irclogs/

For one thing, if you're in a Skype group, you get all group chat history next time you log in, whether you had it running or not. Not so with IRC.

Why not XMPP?