I learned that lesson by making a (what I thought was fairly respectful) joke about Mark Zuckerberg. I get my share of upvotes and downvotes, but that was the fastest I've ever seen it hit the floor. I'm not really a fan of the whole karma thing, but I think my biggest complaint is that when you post, it starts as 1, but doesn't change your overall score, so it's really 0, which would make more sense to me.