Makes me glad that I live in the UK....
4 GSM networks, 5 UMTS/HSDPA networks, using the same frequencies as most of Europe.
It's certainly very nice to change networks in seconds, with a choice of thousands of devices and no operator crippling (and Nokia/SE make it very easy to undo any that happens).
None of this faffing with "opening up" networks.
Vodafone owns 45% of Verizon Wireless. You can bet that they'd be doing the same thing in the UK if the government would let them.
Not regulating which technologies mobile phone companies can use lead to a multitude of incompatible networks (GSM, UMTS, iDEN, CDMA2000) in the US.
It also, however, lead Qualcomm to develop IS-95 (CDMAone). In Europe, that never would have happened, because everyone was required to use GSM.
Guess what? Large portions of UMTS are based on technologies developed by Qualcomm for CDMA.
So, yeah, I guess I'll put up with only having two national GSM/UMTS provider choices (T-Mobile and AT&T).
Regulation always has consequences. Some of them are good (compatibility between networks). Some of them are bad (stifling innovation in new mobile technologies).