Can't they blacklist shipping addresses and/or credit cards? These people open new accounts for a reason; I'd think Amazon could connect and analyze data to discover and mark/blacklist scammers.
Hard to stop with pre-paid debit cards and PO boxes or mail forwarding services. It'd be pretty easy to just open a new one PO/forwarding address and use a different pre paid debit/VISA gift card to keep scamming.
