As long as the payment is valid, typically the seller is in a better position than a buyer for not getting duped. At the same time though, it's good to keep good documentation on the shipment and things like signature confirmation can be a good adder in case the buyer claims he never received it. Not foolproof of course, but it helps. Finally, if it's an expensive item (> std. value they apply, which IIRC is around $300) buy the "insurance" from the shipper just in case something happens in transit, so you can get your money plus refund amount to buyer.