Money order fraud is particularly prevalent on auction sites such as eBay. Below is information on how these scams typically work and what you can do to prevent being a victim.
eBay seller-of-expensive widget receives message from successful buyer, asking if seller will overnight express the expensive widget, if buyer quickly sends a money order with extra funds for the express shipment.
The seller agrees. Money order appears quickly. Seller ships the widget immediately after receipt of the money order.
The money order is later found to be fraudulent, and the seller loses both the expensive widget and the money.