Well, the people who lived in our new house before us must have known that so they left ALL their nails and screws in the walls (and ceiling). Their doesn't appear to be any rhyme or reason to many of them but instead of complaining about it Josh and I have been able to kind of make a game out of it.
It's called, "Find a nail, Find a frame". The object of the game is to see how many things we can get on the walls without actually having to make our own holes. It's really worked quite well.
We officially finished our house today and are all moved in, wall hangings and all. I personally only made 5 new holes=)