Usually an
admission by a user who knows
what the hell he's just done... which is an admission that he's either written a
virus, or a program that he KNOWS will cause problems if it has ANY
bugs.
Sometimes also said by a user who fears the idea that maybe, just maybe, he really did write bug-free code.
(But for some reason, I don't think this is what the person who wrote the Internet Worm said.)