I wouldn't write off listservs yet. I can't speak for academics, but I belong to several very active email groups on various topics. I hope they don't transition to Twitter & Facebook formats. The character limit on Twitter can't possibly lend itself to any kind of real discussion, and with Facebook it would be difficult to maintain the separation between one's family, social, and professional lives that is essential for mental health. My mental health, anyway.

I wonder if anyone has begun to study the impact of Twitter and instant messaging on productivity in the workplace? It must be much more difficult for employers to monitor than internet usage.