That Knobe effect that was mentioned sounds like people weighting negative effects more than positive ones. People often take things for granted until there's a problem. It's possible troublemakers are judged more harshly than problem solvers.
From what I just read, it doesn't even sound that deep.
If you ask me whether a good act was "intentional", I'd assume you mean whether the good effect was the purpose of the act. But if you ask whether a bad act was "intentional", I'd assume you wanted to know whether the bad effect was known in advance. That is, there seems to be different connotations for "intention" in relation to good and bad intents.