It is much easier build merchant rating services/databases than customer rating services/databases. Proof: compare (1) buying from a high-rated eBay seller which is pretty much riskless, to (2) the complex consumer credit rating industry which is doing a poor job at maintaining fraud at constant levels (fraud increasing year over year, small merchants going out of business, etc).
Therefore I assert that the Bitcoin model is superior: solving the fraud risk for merchants is more important than for customers. If a merchant start delivering poorly (or not at all) with purchases, he will quickly receive poor reviews and go out of business, hence self-correcting the fraud problem.
Of course another option with Bitcoin which you are not thinking about is to use escrow services as third party between buyers and sellers.
Therefore I assert that the Bitcoin model is superior: solving the fraud risk for merchants is more important than for customers. If a merchant start delivering poorly (or not at all) with purchases, he will quickly receive poor reviews and go out of business, hence self-correcting the fraud problem.
Of course another option with Bitcoin which you are not thinking about is to use escrow services as third party between buyers and sellers.