We can be honest, AT&T is pretty much a one trick pony with the iPhone exclusive. Without the iPhone, the wireless carrier has some other smartphones and devices that are interesting but with the iPhone generating 3.2 million activations in Q2 2010 alone, that single device is hugely important for AT&T's bottom line.
We all know that the iPhone will be freed from the AT&T chokehold eventually. At that point, most expect to see the device land on rival Verizon giving iPhone fans an out from the issues plaguing the device on the AT&T network.
AT&T's SEC filing hints in several statements that the iPhone exclusive is very near the end of its run. Things are said in the filing like an entire section devoted to risks when "exclusivity arrangements end" and assurances to shareholders that the loss of the iPhone wasn’t seen as a "material negative impact" and customer turn over wouldn’t necessarily increase. Moving carriers is a pain for customers, but AT&T has a lot of iPhone user ire working against it and there are many customers counting the days until they can leave with their iPhone.