As was previously mentioned, AT&T has officially begun unlocking iPhones. Of course, that does come with a few (sort-of) expected catches. For example, the iPhone must not be tied into any agreement and second, the account holder must be in good standing with AT&T. That being said, you can read the official statement from AT&T;
Beginning Sunday, April 8, we will offer qualifying customers the ability to unlock their AT&T iPhones. The only requirements are that a customer’s account must be in good standing, their device cannot be associated with a current and active term commitment on an AT&T customer account, and they need to have fulfilled their contract term, upgraded under one of our upgrade policies or paid an early termination fee.