Another site I chat on (sports related) uses upvotes and downvotes, and each user has a running point total. You get a point for every post you make, upvoting others costs you nothing, downvoting others costs you one point.
Point totals show longevity and frequency of posting, but the negbangs also help the board moderate itself. The truly abusive are hit pretty hard...they tend to leave or adjust their tone a bit.
Right - that too but people usually write their opinions on a post anyway.