And one should not assume money orders are valid. I've had plenty of folks bring in money orders that looked pretty good but were forgeries. Apparently the crooks don't know all that much about them, either, since they often have sequential serial numbers. Real money orders do not issue in sequence.
And while most attempts are crude (and still fool many people), expect them to get better at it. Since their overhead is very low, I expect to see more modest amounts of money involved, better English composition, more believable email addresses, more scams coming from outside the infamous areas (Nigeria, London), more reasonable scenarios (fewer things like inquiring about an ATV to be shipped to Europe) and more specialization, actually knowing something about the sort of goods involved and how to better look real. You can hook a lot more people with $500 transactions with a $50 overage asked to be sent back than you can with $5,000 deals with $2,000 overages, and if you ship the goods, too, they have real stuff to offer someone else in a straight up fraud or just to resell in a straight deal.