I'm not sure if vBulletin has an add on or what not but a rep system may be a nice addition. The rep system will be based on someones posts. If you like the post, you give them a thumbs up or a +. Don't like the post give them a thumbs down or a -. Of course there is the concern of it being abused. This is when you set a limit. Only x amount of rep points maybe given in, lets say 10 or 15 minutes.