All sellers need to use the ebay Unpaid item process and put in place buyer/bidder  blocks.

Block all buyers with 2 unpaid item strikes in a 12 month period and they wont have the right to shop with you. Sure it may penalise some but if all sellers do it there would be a reduction in non payers as they wouldnt be able to use ebay. It would also make them realise that buying/bidding is a contract which has to be finalised.