This recently happened to me and for the briefest moment I thought you know what, I would really like one of these, I could just keep it and get the screen fixed for a lot less than an iPhone would cost. I picked it up of course, figuring I would hand it in at reception or something later, only to discover the owner a couple of meters away frantically searching their bag for it.
I handed it over and felt proud that I had done the right thing, but it was interesting to be in a situation where I had to make a decision like that. On the one hand I would have thought if I could get a virtually free iPhone, for once I was having good luck, finders keepers etc. On the other hand, I would expect myself to do the nice thing and never forgive myself if I didn't.
So, what would you have done in the same situation, and why?