Yeah, thats the point. Buyer: sell me some bitcoins! Seller: ok, plus you get a free cert! Send the payment to this paypal address... Buyer: sent! Seller: ok, your certs in the mail! Buyer: what about my bitcoins? Seller: what bitcoins? Paypal sides with seller who provides proof of shipment.
Will Paypal really side with the seller if the buyer claims the item wasn't as described and he shipped the certificate back?