Unlike many of the people posting here, I am actually in classes in which people bring laptops, and use them to watch youtube, play WoW, and Facebook. However, I don't find myself distracted one bit. If you find that you cannot divert your gaze from the excess flashiness of someone's game of WoW, or the boring details of their Facebook friends, then you have bigger problems than your classmates. Also, why should the professor care if people are paying attention to him? It's their money. Oh yes it is, even with financial aid. Do you really think they are going to continue paying for your education when you start failing classes? I think not.
Aside from those obvious points, there remains the many ways that laptops in class can help. For example, I've taken a laptop to one class in order to use wikipedia to fill in various details missed in the sporadic and rambling lectures of some professors. I download the powerpoint slides used by the professors so I don't have to strain my eyes trying to read badly-focused projected text from the back row (I sit in the back row to avoid distracting people, and I hate it when people look over my shoulder anyway).
Luckily, the students still hold enough of a say at the university I am attending that such ridiculous measures would never fly. But if my professors DID demand that laptops be absent from the lectures, I would be one of the few to actually be affected. Those now playing MMORPGs and Facebook games would simply find another source of distraction - perhaps cellphones (remember those? I hear they have 3D networked games and Facebook now. Amazing.) Those distracted by the laptops of others will simply find some spot of dust on the wall to attract their attention, and still not learn anything.