buyers/sellers that DEFAULT on contract

I have had many deals fall apart when I am selling here on audiogon. There are a lot of flakes out there. I've heard every excuse except the "dog ate my email" and I'm not even a dealer. Cables seem to be flake magnets. But the most outrageous one where some one was agressively bargaining with me over a piece of equipment while he had listed the exact same piece of equipment on ebay, at a time identical to his first email to me, and with a reserve of my asking price! A few things I do. If there are multiple offers I let the second and third person know they are on the list if I don't receive funds. I mark the item sold and keep the ad up until the deal is completed. For all COD's I require good funds in advance for shipping and handling plus 10% non-refundable deposit. No funds in 48 hours, I'll sell it to the next person. I disclose this up front but dealing with these people is always annoying. Now I'm more likely to cut a curt Dealer some slack after about two years here.