I was on a different fourm site and I saw that the people were selling other things than the site was made for...
A paintball fourm website that sells and trades guns, air tanks, barrels etc. amongest the members of the fourm. They could also sell/ trade dvds, video game systems, mp3 players, etc.
Of course if you engauge with buying/selling/trading with another person you run the risk of getting ripped off.
Just a suggestion if people are looking to sell things