<i>the addition of the iPhone 5 could do more to increase smartphone sales among Sprint’s current subscriber base — and put more stress on the carrier’s network thanks to its unlimited data plans — than it will to attract new business</i><p>As a long-time Sprint customer (10 years), this is the most worrisome part about the impending iPhone 5 launch. All those Sprint customers who resisted the urge to get a smartphone, or who have BlackBerry, WinMo, or early Android devices whose contracts are coming due might jump to the iPhone. That could be disastrous for Sprint's network, since iPhone users have been known to be very data-hungry.