It is natural that Apple would look to ATT as a distribution model so they can deliver advanced features.
It benefits the consumer and of ATT/Apple.
When the other networks have the ability to support the advanced features of the IPhone, it is likely that Apple will include them as part of their distribution model.
However, it should be noted that other manufacturers have exclusive arrangements as well. For instance, the Motorola Q9 is offered exclusively on the Sprint network.
There is a rationale for offering products and services unique to the competitor as they see advantageous in acquiring new customers and retaining them
IMO AT&T has not handled their iPhone deal in away that engenders customer loyalty. They didn’t have MMS ready for the launch of the 3.0 OS and their bogus refusal to allow video streaming for the SlingBox app over 3G is an insult given my expensive “unlimited” data plan. Plus Verizon just has better basic coverage overall. There will be a mass exodus if Apple ever cuts a deal with another carrier. That said, the government has no place in this type of business decision. Kerry is just trying to glom on to hot story as usual.