I was a co-admin on a forum and we added "Mojo" to the site with a hack. A script ran every night that chose 100 members at random who have been active in the past 30 days and gave each person 5 mojo points. They could spend mojo on any post they wanted. (not their own). If any post got 3 or more up mojo's it turned green and stood out in the thread. If a post got 3 or more negative mojo's it got squashed. At midnight all unused mojo was cleared and new members were chosen.
Moderators got 25 points and admins got unlimited. This allowed us to make certain posts stand out (turn green) if we felt they were really good.
It worked pretty well actually and we collected some good data on our members. You could really see who the popular ones were and who were the "trouble makers".
Eventually we upgraded the site and the hack went away.