its monopoly on the iPhone may be ending. Apple reached an agreement with Verizon in 2010 to make an iPhone that is compatible with Verizon's network. Allowing Verizon to offer iPhone service will more than double Apple’s market for this device, but will undoubtedly drive some AT&T iPhone customers to Verizon in the hope of finding better network service. Verizon is further hedging its bets by offering leading-edge smartphones based on Google’s Android operating system that compete well against the iPhone. With or without the iPhone, if Verizon’s Android phone sales continue to accelerate, the competitive balance will shift again.