While I have no conceptual problem with that, it only really makes sense if you pay for bandwidth. Right now, I pay for "internet @ speed". I think your model would work if I paid for "100GB of Internet @ speed".

The argument against it, which I am O.K. with, is that the carrier would bias consumption toward established brands, and that would set up competitive barriers to entry for new companies. This would theoretically reduce consumer choice and decrease competition, eventually raising prices. (after all, if the carriers just recoup the costs from Netflix, they'll eventually pass them along to us.)