Also, data caps are just price discrimination, which is pervasive even in highly competitive markets (and not necessarily a bad thing): http://else.econ.ucl.ac.uk/papers/uploaded/222.pdf. You walk into Home Depot and they charge you twice as much for the "Best" paint rollers versus the "Good" paint rollers. It's not because there isn't competition in the paint roller market, or because it costs twice as much to make one paint roller versus the other.