Originally Posted by
akochan
Oh also, because the stretching on a chain is not even, try "rotating" the chain once and a while to put the stretch in another spot and you might eke out a little more life in the chain without one of the links breaking (as one also must do with that skid spot on the back tire

Sources?
This sounds more reasonable:
http://www.sheldonbrown.com/chain-life.html