Can you switch carriers (AT&T to Verizon) with the new iPhone 4S?
From what I have seen, this is true of any carrier subsidized phone in the US and the FAQ also indicates the unlocked versions they plan on selling will be AT&T compatible only. The key is not what the phone can do but what the carriers dictate you can do in your service agreement when you activate service with a them. None of the major US carriers have shown any indication in the past to be willing to sell truly unlocked phones.
In addition, AT&T, Verizon and Sprint are all deploying LTE in a different spectrum, so they will have even less incentive to make phone compatible on competitor's networks.
When I purchase a TV, I am not restricted to a single Cable provider nor satellite ON THAT TV! I can use that TV set any way I like. As a person who often calls himself a fiscal conservative, who believes in the power of a free-market, I find myself quite often frustrated with large mobile phone carriers.
And in this case, carriers like AT&T and/or Verizon are implementing practices which prevent free-market principles from taking place. If your service was the best, you would not have to worry about people switching carriers. That is why we have competition. Because it inspires innovation and yields better service.
These rules make me ill. Sorry for the rant.
At least we have two year contracts. Three years is the norm up north.