Yes, only point 3 is a threat and its not very likely. I only think a scammer with address in china and paying by paypal has no risk to fear at all. One would think that no buyer will abandon his chips and not order assembly but when i see how many billing addresses still are missing in my groupbuy i wonder what those buyers do.
On the other hand. Everyone that fears to be scammed only has to order the assembly before the chips arrive with burnin. Then he is safe. Of course only when you mark in your list when chips are wanted to be verified by burnin. I doubt that burnin would check for duplicate orders in his shop. Thats something the group buy organizers have to do.
Its only a risk that applies to lamers that dont order assembly before the chips arrive at burnin.