Several years ago while walking outdoors during the winter carrying my thinkpad in my hands, I slipped on a manhole cover that was covered in ice. The thinkpad fell about 4 to 5 feet straight onto the manhole cover, landing on it's corner (left-side palm rest corner).

The corner itself was obliterated, leaving a small hole where it used to be, but that was the only damage the laptop sustained.

Unibody metal laptops are nice, but I think the structural advantage of them is heavily oversold. Plastic laptops with metal frames can be amazingly durable.