Republicans.
How sad it is that so many people want the government to be their momma and papa. For goodness sake people, you know what the deal is before you buy the phone, and if you don't like it DON'T GET IT! It isn't the responsibility of government to make all products available to you in the way you want them.
Don't want to get fat? Well, screw the choice of not eating at KFC, let's get the government to ban transfats! Hmmm, I wonder if the government would mind stepping in and mandating that Bravo find some way to get a high-def signal to my house so I can get the network in HD, since it is available with DirecTV but not my cable provider. That just isn't fair, darnit!
Let's look at some basic economics here. In a free market, what do you think is going to happen since the iPhone is locked in to AT&T for 4 more years? Do you think T-Mobile, Verizon, and Sprint are going to go into their respective closets and hide until these 4 years have passed? Or do you think they are going to say, "Screw this! We will develop a competitor to the iPhone!"
If you said the exclusive contract with AT&T will spur development of new phones, move to the head of the class. If the iPhone was available on all networks there would be no incentive for these carriers to invest in new technologies. Further, what will happen when new phones are developed? Why, Apple will have to improve the iPhone to keep up and AT&T will have to lower the prices (or resist increasing them) to stay competitive.
The reason wireless companies can get away with contracts is because people sign up for them. Stop signing up for contracts (use a prepaid service) and they will have no choice but to do away with them.
Within the next 18 months there will be a boat load of iPhone-like devices to choose from, and they will all be cheaper than the iPhone/AT&T combo is now. In response Apple will be forced to dramatically improve the iPhone, and everyone will be a winner....regardless of what cell phone carrier you are with.