In reading articles and the like the issue of trust between buyer and seller is glossed over.  BitBay purports a certain sum held in contract by both parties is an unequivocal gurantee scamming won't occur.  To me, it seems unless that amount is 100% of the agreed purchase price it will stack the deck against sellers and invite buyers [scammers] to purchase goods at a discount.

For example, lets say someone has a comic book for 10,000 BAY with collateral of 1000 BAY.  What's to stop the buyer from saying he never got it, sacrificing the 1000 BAY, and essentially get the comic at a 90% discount?

Or is the problem the opposite?  I.e., once funds have transferred to the seller, is the onus then on the seller to issue a refund if the buyer has a problem?  Flipping the script, what's to stop a seller in the above senario from selling a buyer an empty box for what amounts to 9,000 BAY?

This collateral system is offered as a panacea to limit or eliminate fraud, but I can't quite see how it will work in practice...