I put an ad on craigslist for a bed a few days ago, and somebody said they wanted to buy it. This person (Dave for explaination's sake) said he will send me a money order in the mail, and upon recieving the money order the shipping company would come pick up the bed. This morning, I recieved an email from Dave saying that his assistant accidentally sent my money order to somebody else, and sent somebody else's money order to me; and that upon recieving the larger money order, I should cash it in the bank and then use western union to wire the remaining balance to the manager of the shipping company. Is this a legit practice or am I getting duped. As time goes on, the situation seems more and more fishy, so I turn to you all for advice.

::Edit:: Thank you. I'm not sure why I even let the idea of this being legitimate enter my brain, but you guys are there to slap me back to reality! Thank you!

Update: Even after I changed the ads yesterday to say 'local only, cash only' I have recieved 3 emails that claim that cash won't work, but they'll gladly send money orders. Is this amount of crap common on craigslist, or am I just really unlucky? P.S.- I told them no.