I can buy *any* TV I want then get cable or dish service from *any* provider I want.
I can buy a computer from *any* company and then get Internet from *any* provider I want.
I can buy a land-line phone from *any* phone maker and then get phone service from *any* provider I want.
Cable: exclusivity deals with towns, limited, if any selection
Internet: exclusivity deals with towns, limited, if any selection
Phone: exclusivity deals with towns, limited, if any selection
Not to mention these three are usually the same company...
I get your point though, I currently have an iPhone from AT&T, but I'm doing some development work on the G1, which conveniently supports all the 3G bands but AT&Ts, and the iPhone supports all the 3G bands but T-Mobile's...