Just a thought - how easy would it be to add a "thumbs up" or "thumbs down" ("good comment"/"bad comment") facility to peoples' posts/questions -similar to the Youtube one?
Could be a fun and if certain posts/questions generate lots of "thumbs up"s it might up the kudos stakes.
MM
The problem is that people don't "thumb up" a good reply, just one they agree with. If they agree or disagree, much better that they post an answer stating why. Otherwise, what was a discussion just becomes a mob of voters with nothing to say.