I understand the "why" but not really the "need" for doing this, because the "need" seems to be one of pure "Greed" on the part of bidders who are willing to do something that is against the Rules but figure if they can get away with it then why not.
It has nothing to do with the greed of the bidder. If a guy bids on a gun, he probably wants it. If the seller contacts him and says he suddenly needs money and will take the bid amount, how does that make a bidder "greedy"? The bidder wants it, the seller is willing to sell it, he tells the bidder he will end the auction as soon as payment is mailed, and that would make it a done deal with GunBroker. GB allows auctions to be ended, IF the gun is sold to the high bidder after a reserve, if any, is met. They take a commission on that amount, and no rules are broken.
It works like this:
The scam artist contacts my high bidder, claiming to be me. The scammer(claiming to be me) would tell the high bidder that they have decided to sell the gun for the bidder's current bid amount. If the bidder said OK, they would tell the bidder to mail some form of quick payment or a wire transfer to them.
Till an auction is over, most bidders do not know the real name of a seller, so there is always a chance it might work. If a scammer sends out 300 emails, and only one or two work, he still has a pretty profitable week. After all these years, why do you think we still get the emails telling us we have won the lottery?
4 or 5 of the bidders in my last auctions were contacted by scammers. Fortunately, all of them were smart enought to click "Ask seller a question", and contact me about it.
We reported them all to GunBroker. The same thing used to happen on ebay. There are many people in the world that sit at keyboards all day trying to scam honest people.
Of course, I see your point about bumping heads with a friend. A few crooks will always make it tough for the rest of us.