Apparently there are some bogus Postal Money Orders being passed. When I take a MO to the post office to cash it, the girl behind the counter holds it up to the light and generally looks it over real well. We also had some crooks using forged bank cashiers checks to buy used cars around here. They would buy the cashiers check for a small amount, bleach the $ amount and reprint that part for the big $$ purchase price. In one case the bank affirmed their cashiers check was good, only to reject it 3 weeks later.
One time when I sold something to a customer in the Philippines, he sent me payment in cash USD in a birthday card. I've had other customers send me several hundred $ in cash, too, but we know each other and they "know where I live." Paypal is preferred but I accept anything.