The mobile market in North America is badly fragmented, due to
different carriers using different technologies (CDMA vs. GSM), different frequencies for different companies (AWS, 2100), and locking of phones to the carrier.
This fragmentation strengthens the stranglehold of the carrier on the customer, who has a higher barrier switching from one company to the other.
Industry lobbyists still call for more balkanization of the market, by adding more frequencies, against standardization.
This has starting to cause some of the large monopolies to offer cheaper alternatives.
This is all good for the consumer, minus the fragmentation of handsets part ...