Without looking I'd be nearly certain that Amazon isn't going to take the hit for chargebacks on the marketplace. Appart from costing a heap it would just be inviting fraud.

If they're like paypal they just don't contest and pass the hit on to the seller unless they can prove otherwise.

Yeah, I have found PayPal for all their supposed fraud protections to be quiet useless with preventing chargebacks. As a merchant you are also disadvantaged in that you aren't able to access any BIN/AVS data on the card yourself.

No. To their credit Amazon eventually did end up eventually sending us a new copy of the DVDs, but it took quite a lot of effort to make that happen.