I actually read an article on this sort of thing a while ago. People are using selling sites to "sell" a product that they don't have.
They recieve the money use it and when they are paid themselves they return the money to the buyer with a reasoning along the lines of "i damaged it" etc. The buyer gets their money back in good faith and the seller hopes not to get a bad review because they were being honest about the damage and returned the money.
Payday loans but without the interest.