No, all these can easily be prevented. In fact these has been prevented by brick and mortar shops fairly reliably for decades. Online sellers can impose background checks, identity verification, automatic law enforcement reporting, security deposits, delayed payments etc. One shouldn't be just able to post a product listing with intentional falsehood and omissions, sold openly to public and get away with it. That should be and is a bonafide crime. A system that allows that is helping to support and proliferate that crime.