If you did do something like this, a sub-forum or such, you would state that you are merely providing a means for interested sellers and buyers to get in contact with each other. You have no relationship with either seller or buyer beyond that. What the buyer and seller agree upon and how it is carried out is beyond you and your control. The only thing you would have to watch for are any flames, etc.. if anyone does become disgruntled. Since EoFF is not taking a cut of any sale and has no business relationship with either party it's easy to stay out of things and keep your hands clean, as opposed to eBay, who has a business, and legal, relationship with buyer and seller.