I've been resisting it madly, but (again) Gerd Leonhard makes an impassioned please: use twitter or wither.
midemnetblog.typepad.com/midemnet_blog/2...eting-tool.html#more
Two other things I've noticed, LinkedIn has two very active music biz message boards and Midem has its own message system and online storage of files called MidemWorld (making it like a more sedate myspace for business). They tend to be lighter on grand opinions