Yeah, I do the downvoting thing from time to time. If there are few answers, and I think mine is slightly better, I will downvote them so mine goes to the top. This usually results in lots of points, since people see mine at the top and upvote, and see the others at the bottom, and downvote them. (The same thing works here, but I don't do it. My comments usually get upvoted anyway, for some reason.)

The funny part is that someone "noticed" this and complained to me about it. (There was a whole meta thread about it, which I thought was hilarious.) In that case, though, his answers were just plain bad, and I had to downmod his answer and answer the question myself just so that people would not be horribly misguided by his high reputation but wrong answers.

Anyway, I hate to "game" sites like StackOverflow, but there is no incentive not to. If I get banned, it just means people won't get my knowledge for free anymore. I have never needed to ask a question there; I have a social network for that (which can't be "gamed", btw).

(As to why I care about rep, I don't know. It just feels good to get a lot of points, I guess. It's like winning the lottery, except you can't cash in reputation for goods and services...)