Whenever an "opportunity" arises for less than honest operations to jump in, make a quick buck and jump out unscathed with their pockets full you will have all kinds of people try it. If it works, not only will they keep doing it but it doesn't take long for the word to spread within the criminal world and others pop up. (Scum bags tend to like to brag about their success)
Buyer beware is the only advice. If you don't have a history with them and haven't done your due diligence then you are making it easy for them.