Back in 't' old days' ie 10 years ago before ebay got this daft idea about 'security' bidders could be identified from a listing. If there was something dodgy about a seller you could send a message to the bidders, or tell at a glance if the same member kept bidding on someone's items and never winning. I met two collectors who taught me (almost!) all I know through ebay and it worked well as a community. Then someone started a scam messaging underbidders and offering them the item, which of course the messager didn't have and instead of using paypal and banning those responsible ebay made it impossible for anyone to identify bidders and hence to report the bad guys. It was like using a sledgehammer to crack a nut. The problem with ebay is that they are scared of lawsuits from big manufacturers so any hint of fake Gucci or Levis and they will act. But coins .. they have no expertise and as most of the time nothing happens, they do nowt. If buyers started to sue ebay for assisting fraudulent activities, things might change, but .. And as for warnings, I guess one way would be to copy the technique of an Ameican medal expert. He has a listing on ebay for one of the medals most commonly sold as a copy for a high price as a buy it now. When you read it it isn't a sale listing but a guide to spotting fakes and a warning. Whether his reputation means ebay allows him to do this or it doesn't care but it must be one of the only listings left on ebay.com that says 'fake' in the title!