While CIOs might gloat at BYOD's perceived cost savings--no more BlackBerry purchases!--they'd be wrong to do so. Aberdeen Group found that a company with 1,000 mobile devices spends an extra $170,000 per year, on average, when they use a BYOD approach.

"Organizations that simply say BYOD is about productivity and have completely ignored the cost structure are playing with a blank check," says Aberdeen analyst Hyoun Park.

This is a splash of cold water on the hot BYOD trend.

Mobile BYOD was supposed to get CIOs out of the vicious hardware-buying cycle, or at least offset costs.

Case-in-point: Cisco's cost savings from BYOD is in the neighborhood of 17 percent to 22 percent. "We don't pay for it, and our users are happier," Lance Perry, Cisco's vice president of IT, customer strategy and success, told in the Enterprise Conference and Expo in San Francisco last month. "Isn't that a beautiful thing?"