I saw this a couple of months ago on Popjustice and it looked a little exclusive - it still does. It's essentially from the team that made last.fm (I think!?) where you can share music with friends and strangers in order to discover stuff. There's also the option to rate other members' selections and they can then go on to build reputation (if that's what you want to do... I'm really just there to discover music).
Anyway I decided to make a TiBB room. It says it's invite-only but I just managed to get in by logging in with Facebook (you have to "allow" the Turntable application, it should be quite easy). Here's the room:
http://turntable.fm/4e36529114169c6b5a05f5ff
Up to 5 members can DJ at a time (on a turn-taking basis) and yeah I made this mostly for fun
Only members who have this link can join the room, so don't worry, no randomers
(and please don't give it to others... not that you would anyway, unless you want people knowing about arista?)
I'm the moderator of it since I created it, so no misbehaving or being mean about others' musical tastes
(the IRONY. <3)
edit:
http://www.rolling.fm/web/room2/2832604