It probably just means that some petty fool clicked it when you disagreed with them, knowing that you can't see who gives you reputation.
That's probably a good thing too. Though it might be better if karma actions could only be performed once on each member. For example, if I applaud/dispraise member A, then I cannot alter member A's reputation after that. Otherwise, maybe some guy would keep spamming the applaud/dispraise until at least one person here has +a zillion or -a zillion.
