Sometimes, I outclever myself. I added a simple text filter for screening comments and trackbacks recently. It's a simple filter, and that's part of what bit me today. I had someone ask me why their comment got eaten, so I went to have a look. As it happens, it was chewed up by a stupid entry in my filter. I added "anal" to my filter, due to a bunch of pr0n stuff showing up.
Sadly, I didn't limit that to looking for "anal" with a space after it (and "anal" could be valid, as in "that's a really anal way of looking at it"). Anyway, the comment in question got eaten by the word "analysis". Dumb, dumb, dumb.
It's fixed now, until the next dumb mistake like this I make :)