How about using the "karma" function. I've seen some forums where if someone post something good, people click "applaud" then if they post something not worthwhile, then people click "smite". Not sure if this will work here in our culture, not sure if it will do more good than bad (like make the site more "clickish" than more welcoming). Anyway, just a thought, you may "smite" me if you think this is not a good idea, haha