Similar to Slashdot's?  Individual members (who have good karma from writing good posts) are given moderation points that they can assign to good posts or detract from bad posts.  Your karma goes up with the more your posts are moderated up.  The moderaters are monitored by meta-moderators, who say if the moderation done to a particular comment was fair or unfair, and the moderator's karma is adjusted properly.

The good part of this system is that you can browse only the comments that are moderated up, or the users with good karma, so you don't see crap if you don't want to.

Its an interesting, albeit a little complex, system that has worked well for the huge volume of posts on slashdot.