Hey I have had that done to me. I sell on eBay and I went in to look at my account, as I do every day, and apparently I was selling 2 ford mustangs in America!!!!
Normally we sell nice boring Antiques, but these 2 cars appeared, pictures and all, all their details on them (I dont know if the details where right, but it sounded good!).
It is VERY common for people who are legit to have this "Account Theft". The reason people do it is simple really, they will be advertising or about to advertise an actual vehicle and will therefore want to push the price up of similar peices to their own. Option 2 is they put the vehicle on your account, and then THEY bid on it and win it. They then send you the money from a STOLEN credit card via something like paypal, then wait a few days and then back out, claiming a refund via paypal. Although the funds came to paypal from a card, the money is returned to paypal and it sits there - they then download the money to their bank account.
I have never bought a car on eBay, but have spent a small fortune on Antiques and stuff like that, and if its an expensive item I only ever send a deposit before I have seen it and pay on collection. That way, worst case scenario, I lose £50. You would also be amazed at the number of people who find excuses as to why you cant pay the balance when you collect...
5 years on that site makes ya cynical and rots ya brain... off to dribble

)