I have seen some people using iPhones where the screen has been broken. Does the glass eventually fall out? Or is there some adhesive on the back that keeps it glued in?
Apple calls it "glass" but it's not that literally. The material used is basically a very hard plastic with glass-like properties, so it breaks a little different too. Apple uses a very good adhesive to keep the "glass" adhered to the lcd below it. I've only seen glass fall out on the upper/lower bezels not near the screen. But as was mentioned, it depends on how badly it was damaged. There certainly will be small bits of the glass chipping off though.