Craigslist Scam!

I've been trying to rent out the upstairs apartment in the house to make up for the lost June and July rent. I've had some interest, and I thought I had found a great couple who wanted to use it for a long weekend during a vacation to the US:

Hello,
My name is Bob Draper,I will like to know if my Wife and i can spend 3 nights at your place.We will like to know if you have July 7 to 10 available.I will like you to get back to me with the cost and availability.

Thanks

Sounds good, doesn't it? So I emailed him back, we negotiated a price, he asked for more details and I sent him a loooong email describing the apartment in detail. Then I get this email:

Hello
How are you today,i am happy to inform you that the payment has been sent to you and will deliver to you soon.I was informed that our travelling funds was included to the money that was sent to you for booking and this was supposed to come in a different check that was supposed to go to our travel agent.But since it has been sent,as soon as you get the check,i will like you to deduct the full cost for the booking and get the excess money to our agent and due to the short time before our arrival,i will like you to send the money to the agent through Western Union so that she can do all neccesary things pending the time of our arrival.I hope you understand this and we can be able to depend on you.

Thanks

At the words "excess money" and "Western Union" my scam-radar went off the charts! It goes without saying that I put an immediate end to communications with this individual. But it piqued my curiosity... how exactly does anyone make money off of a scheme like this? The best I can figure is that he would have sent a fake cashier's check, and apparently some banks will cash these and then hold you liable later when they are discovered as frauds. I guess the schemers hope it will all come down on you long after you have wired them funds. It's still sort of baffling to me that anyone falls for these things...