Any "market" or "marketplace"-----whether it's online, like ongait, PEM, or whatever, or a live auction like the old Tully/Woodstock, PEM, Tattersalls, etc.-----can never be perfect. It is going to offer the opportunity for unscrupulous people and activities. It is the market-maker, auction/sales company, whoever, to do everything they can to protect the buyers and sellers.
Now, if they don't do that, it will become known, and then people will stop using them and their market. Even with that, in every market, it is still buyer beware, and the buyer can and should do everything they can. The former doesn't change the latter.