Flip phones seem pretty popular these days. I wonder why. After all, the hinge is just a weak spot in the structure of the phone. It also adds complexity: the electronics are split between the two halves of the phone and wiring is run through the hinge, where it has to flex every time the phone is open and shut. Of course, the main display is on the inside of the phone, where you have to flip the phone open to see your caller ID. To fix that problem, there's a second display on the outside of the phone. Why, exactly, is this a good idea?