It is difficult, or impossible, to get your money back after a deal goes south if you paid by Moneygram or wire transfer. A common scam is as Sean described, "Anyone with a WTB ad gets contacted saying they have the parts you need. Typically they are in England and many times say their paypal is dormant and they request a moneygram be sent."
Sean is right except the problem extends way beyond Porsche parts and Pelican - the scammers can be from anywhere and claim to have anything they think you want. There is a fairly active guy working in Western Pennsylvania doing this with all manner of items. We've been chasing him for years. He knows the system and knows that if he rips someone off for less than $1000 the local authorities won't pursue it, so he keeps dollar amounts under $1k. He also knows that if he accepts anything sent through the mail he is guilty of mail fraud, so he will not accept a money order sent through the mail.
Parts Sales Fraud - SmokStak