Forgive my ignorance for things all IRC, but what about the chat room for the GWJ Steam group? Its always empty now, but it seems like it could be a pretty good ready made meeting place.
IRC is much more versatile, most important is that it can be accessed from everywhere, not just where you can run Steam. Twitter on the other hand is like the bastard child of a forum and chat, but not a straight up replacement for either.
Anyway, could be worth seeing if there's any interest. I'm no IRC fiend by any means, but over here Quakenet was always where anything gaming related was located. I'll be idling in #[email protected] and anyone is free to join.
Here's the server list (random US server: gameservers.tx.us.quakenet.org:6667) or you can use the web client by just choosing a nickname and clicking connect.
I expect it to be pretty slow at catching on, if it does, since it's likely to be prone to a moment 22 effect where people log on, see very few people on and immediately log off.