The whole concept reminds me a bit of the "bagel guy" in Freakonomics. If I remember correctly, he had an ~85% payment rate when it was strictly on the honour system.

I'd be curious to know their payment rate. On one hand you'd expect it to go up since they actually have the name and e-mail address of the buyer (the bagel guy had nothing). But on the other hand, the whole impersonal nature of the internet might increase fraud. Could go either way.

(for those who haven't read Freakonomics, the "bagel" guy would drop off a box of bagels in an office and pick up the remaining bagels and the proceeds at the end of the day)