CRAIGSLIST has a notice in the heading of their postings warning about ANY transactions asking for western union or moneygram.
"Avoid scams and fraud by dealing locally! Beware any deal involving Western Union, Moneygram, wire transfer, cashier check, money order, shipping, escrow, or any promise of transaction protection/certification/guarantee" Craigslist warning
But as PT Barnum said, "There's one born every minute!" they keep posting so there must enough unaware people out there that make it profitable for the scammer.