Just wanted to get a post in here before this gets locked.
I actualy will agree, that I also beleive once you have a buyer, you should stick with that buyer, after you exchange addresses, I beleive that is as good as a handshake, and if you can't follow through with a deal, you need to PM the buyer/seller immediatly and explain the situation in detail, apologize, and then mabey even contact an Admin. to inform them of the sitituation just so they relise that if anything has happened/will happen, you would prefer to keep your PRIVATE MESSAGES private,etc. Also, they won't be suprised when a thread like this comes up,etc.
I also beleive there needs to be a feedback forum, I'm sorta actualy uncomfortable that there isn't one. I relise a seller might have one veiw, and the buyer another, but still, there isn't one way to inform the forum that a seller/buyer is fraud,etc. Don't know think that this would help other buyers/sellers judgement? Or, instead of leaving a negative feedback,etc. Positive deals could just leave a kudo,etc in a member's profile. So the more kudos a member has, the more reliable. Instead of having a "negative" feedback, the member would just have a number of positive ones.