If you know the people who are selling marbles on the Facebook Marble pages that allow sales, you should be in good shape. Also, as sort of a policing measure, if there is a problem on a FB sale, it gets posted on the page and that seller is toast for selling more - unless they correct the problem. But, as Ron says, no "insurance", etc. except if you pay by Paypal using goods and services (not family, friends), that will give you some protection.