Source : PCWORLDPC World decided to try and break the iPhone during several stress tests, including shaking it in a bag full of keys and dropping it on concrete.
Here is their conclusion:
The iPhone not only continue to work after each drop test, impressively it still looked good as well. The only obvious damage suffered was a few gouges along its metal edge from the concrete drops. But it came out without a scratch on its glass screen, despite our best efforts to mar it in repeated tests of both types.
Sorry iPhone bashers, but it seems there won't be any "This is cr*p, it's all scratched" debacle like there was with the first iPod nano.