It's actually not too unusual. Perhaps this story in today's newspaper describes the most common scam.
all i can say is... wow. i don't want to elaborate any, because i'll just say things that aren't very nice and probably end up offending someone's delicate sensibilities.
maybe for the newer generations who only know paypal, credit, debit, and atm these things can happen, but back in the old days (this is kinda sarcastic, cause i'm not terribly old) i remember buying many things through mail order and paying by personal check. anyone who remembers this will also remember that any time you paid by check you had to wait until the check cleared before the item would get shipped. this was standard practice everywhere.
if i got a check for more than 5x what it should have been and they asked for a refund, i'd probably have just mailed the check back, or taken the check and envelope to the police, cause it's just absurd. if i had cashed it due to some lapse in judgment, i'd have said sure, i'll refund you the money once your check clears, or you can pick up the balance when you get the couch. at some point we've got to rely on common sense breaking out and not waiting for people to pass legislation to protect us from our own stupidity.