Facebook Instant Messenger -- Will class ever be the same?

As reported by CNN, Facebook launched an instant messenger chat application today, which looks to be a massively popular addition to their burgeoning social network. Students spend a good deal of time on Facebook during classes or as a distraction from JP's and Theses even without a substitute for AIM; I can hazard a guess that this new feature will exponentially increase Facebook's appeal and the distraction it provides. Thoughts from Facebook addicts or professors who want to ban laptops in class are welcome below...