Its a little embarrassing when you spend a few hours tracking down a bug that happened to be caused by some changes you made a year before.
And it's even more embarrassing when you spend half an hour shouting at a cow-orker to clean up his act, then, when he asks what the hell was all that about, you actually use CVS annotate to find out that the problem was caused by your own changes of just about two weeks ago...
Fortunately, a couple of beers after hours were enough to make up, though I still shudder at the memory.