One idea for a forum contest would be to donate a prize to the member who refers the most users to the site. This can be tracked easily enough in the vBulletin admincp, however if you want to look past numbers, and actually see if these new members become active and are actually legit, how can this be done? Is there any hacks out there which shares more referral data for vB?
Im not sure at vb but at phpBB they have a referral mod that pretty much do the same thing. For contests,don't give only 1 grand prize..You would give 5 smaller prize because people will be thinking that they have more chance of winning and they will try out the referral contest.
I wrote a hack for posting contests. I'm sure one for referals wouldn't be a far reach. Seems like a cross reference to the referees and the post count is needed as well?
Looking into this, I didn't actually realise in the Admincp under the User / Referral settings it actually displays the members for each referral.