Buying and Selling of feedback

Today I saw the second auction where the seller states something to this effect "if you don't come through with payment on a winning bid, you can give me $xx (or a percentage of the bid) and back out without negative feedback posted. otherwise, negative feedback will be posted.

This seems like extortion to me. Also, aren't the rest of us entitled to know about a deadbeat bidder (via negative feedback)? The posting of negative feedback is the correct recourse for a deadbeat bidder - not a bribe or "fine".

I think this behavior undermines the feedback process. What do the rest of you think?

Just curious.