Found this thread via Google search and I wanted to add two items:
1. A house I was in that had been built in 1985 or so had the grounding hole "up" only for outlets controlled by a switch. This was the installer's way of letting you know "these outlets are different." An interesting idea, but I've never seen it done since then.
2. A friend of mine had a shallow, but not completely stable, dish full of spare change sitting on top of her TV... and the TV was directly in front of its receptacle. There was a multi-tap adapter in the top outlet of the receptacle, and its plug was not fully in the socket. One day the dish was knocked backward and coins fell behind the set. Sure enough, a coin landed squarely on the hot and neutral prongs. *blam* So, it *can* happen, and not just from kids with toy remote control antennas.