Saw a chain come into the shop the other day. This girl had never changed her chain in the few years she's had her (very expensive mountain) bike. The chain was SO stretched that it wouldn't even fit on the chainring any more. By the time it got to the bottom it wouldn't seat with the gear teeth anymore. How people let their chains get this bad I'm not sure.

I would let it go, many people don't realize bikes need maintenance, but this girl apparently raced her bike as well.

At one point she said something to the effect of "I was wondering why it wasn't shifting very well."