The reasons some of the other people posted above is why I disagree with adding in a dislike button. My last post was blunt, mainly due to I have a tendency to try to justify my reasons with drawn out posts.

Zam is a perfect example. Being there for a very short period myself, but lurk read all the time, I could see how bad this rating system of theirs is. After time, you see how this community builds out, someone being on the site's good site will always have their posts rated up, regardless of what their opinion is. Any trolls or even NEW people on the site would get themselves rated down because their opinion doesn't match, they're a nobody, or you have the abusers that click to rate down just because they can.

So here's my reason why I don't think this would be a good idea. It's a legit response, and yet I bet that if that feature was in right now I would be rated down because the haters don't like my opinion.