Marketplace idea

On another forum I belong to, they have recently added a marketplace forum similiar to Applefritter's. The difference is that the marketplace isn't at all user visibile until a user has posted 5 times to any of the other forums. This could help limit the number of folks that just sign-up to post spam, scams, etc. It might also help put a few minds at ease to be able to see what kind of posts a potential buyer/seller has made in the past before attemping to do business with them. Of course, it could also increase spurious posting just to gain access to the marketplace. Thoughts?