imagine if this was on Amazon! I really hope this catches on!
EDIT: I stand corrected, you can leave public feedback on the seller's page (it's a bit hard to get there, you have to go through the sold product). That being said, refunding the non-delivered item doesn't seem to be possible without contacting support.
But people also buy tons of brand-name stuff on Amazon, where this can't happen. I absolutely want to know the return rate for name-brand stuff.