I had my iPhone Duo for about six hours and probably opened it less than 20 times.
I was showing it to a friend, and when I opened it, I felt something around the inner hinge, under the screen.
As I continued to open it, I heard an audible crack and the screen broke along the hinge.
There were no marks or damage to the surface of the inner screen or the outer hinge to suggest anything had become trapped or damaged.