A few years ago, there had been a number of scammers of people selling their stuffs for a dirt cheap prices over the web. Once the agreement is done, they will ask you to transfer the money and later you do not receive the products.
There was also one occassions by which I bid for a video camera in this manner. Bus as Tempus mentioned, he asked me to transfer the money through western union and said that the item will only be shipped after he sees the money, that's when I backed out.
These kinds of stories was highlighted is the New Paper a few years ago too. So do becareful.
Yes, do look at the "good" comments made, the different people commented made the same "spelling" mistakes. And in one of the comments, the "buyer's comment" sounds like the seller asking to transfer the money.