The problem is , there is little resolution to a bad buyer anymore, sellers cannot give negative feedback, and scammers can ding your feedback after they scam you. So the users have identified them, but they cant tell anyone.
It is like being at the department store with a criminal in the return aisle, holding up the whole show , with no reciept claiming they bought what they stole.
All the department store has to do is announce over the PA , that another criminal is at thier return desk, and watch half the store clear out.