I've always thought these "email is dead or shortly will be" articles to be wildly presumptuous. The argument is generally that the tween/teen demographic hardly ever uses e-mail, and instead use facetwitsquarespace, hence as they grow up email will die out.

This argument is missing one huge point: what happens when these people go to work? How many businesses will want internal communications delivered over social networks?

Email, although far from perfect, is a wonderful work tool. It's private, it's asynchronous, it's distributed, it's cheap. I don't see this being replaced by social messaging.