Lol, it happens to me too. I am quite paranoid about people scratching and denting my car by opening their car doors onto mine. So I park somewhere 'out of the way' but invariably someone will park next to me even when other spaces are available.
The other similar thing is when you are on holiday and you see a nice parking spot to pull over and eat your sandwiches, no-one else there, nice and tranquil. Suddenly half way through your grub, 10 other cars pull up and have a barbeque :-)