I suppose that some people did buy iPhones because the phones worked on the AT&T cellular network. This is supposition on my part because I have not seen any articles claiming this to be the case nor have I read any blogs commentaries that support the concept. In fact, when the iPhone first came out, about all of the discussion that was not about the iPhone itself but about how annoyed people were that they would be forced to use the AT&T network. There is now a rising chorus of voices saying that such exclusive arrangements are not in the best interests of consumers.

By all reports, the exclusive deal for the iPhone has been great for AT&T. They now have more than 78 million wireless subscribers, up 24% from a year ago, due in no small part to the iPhone. The exclusive arrangement seems to be a very mixed bag for Apple. It has been able to extract concessions and revenue from AT&T far beyond what any other handset manufacturer has been able to do but it is clear that having the iPhone tied to a single carrier significantly reduces the overall sales of the device. For example, Research In Motion's BlackBerry Curve outsold Apple iPhones in the first quarter of 2009.
A major factor may have been that the Curve is available on all four major U.S. carriers. I expect that Apple would actually sell many more iPhones and make much more money if it was not in the exclusive arrangement with AT&T. But Apple would have less leverage on what kinds of packages the carriers offered and likely would not be able to get as much of a revenue stream from post sales payments from the carriers.

Apple has gone further that many people like in trying to enforce the exclusive arrangement. Timothy Maun has a good article in the Wisconsin Law Review on the legal non-niceties of what Apple has been doing. (See "IHack, therefore iBrick: Cellular Contract Law, the Apple iPhone, and Apple's Extraordinary Remedy for Breach" here.  

Acting FCC chair Michael J. Copps has announced that the FCC will open a proceeding to "closely examine wireless handset exclusivity arrangements."

Incoming FCC Chair Julius Genachowski has indicated support for this investigation. Congress has also gotten into the act -- for example, Sen. Kerry asked Genachowski to answer a question on handset exclusivity as part of his confirmation hearings.