Go with your gut feeling - it's never wrong. And remember, U.S. Postal Money Orders, bank or cashier's checks, and any other form of paper payment (including U.S. bills) can easily be counterfitted on a laser printer. If you sell a lot, it might be a good idea to ask someone at your bank to show you how to recognize fake bills. If people are big into scamming, you know they are set up to do the fanciest of print jobs to that end.
It's good that people are recognizing these patterns scammers use - like being out of town on a business trip, having their men pick it up, etc - it is those patterns that give them away, once people begin to catch on. Then they'll have to dream up a new scheme, and we'll have to figure them out, too.
As my father used to say, and so many on here have said, if it's too good to be true, it's not true.