There are essentially two main reasons to hold a phone up at a show. First, to capture a memory for yourself, a reminder of the moment you're enjoying. And second, to share that moment with someone - to express your emotions socially. Both seem perfectly legitimate to me.
The hardest thing in the world is to capture the loyalty of people on the Web, and AIM has done that. AIM is a window to the youth market and a platform for so much more than just instant messaging.