I watched an iPhone get a dent yesterday. Not a pretty sight. It was my girlfriends iPhone. She dropped it on the floor, and unfortunally it landed on the edge of a doorstep, causing it to get a dent. Nothing wrong with the glass surface or function of the phone at all.
Ive dropped mine a few times on rocky concrete, without it getting scratches on the glass surface, which has really surprised me. Im sure mine will get a dent or scratch in the future though. Its a piece of equipment, and therefore will get its share of wear and tear.
So to iterate, it IS possible to damage this mythic piece of gadgetry.