This happened in London in 2002. My friend and I were walking along the street in Whitechapel when a guy approached us with the latest top end Sony Vaio laptop which costed around 1500 pounds and was willing to sell it to us for 200 pounds. Us being IT students we were naturally very excited but we only had twenty odd each amongst us. The guy said there was an ATM nearby where we could withdraw the cash and told us to come to the car when we had the cash. My card was having some problems so I asked my friend to withdraw the money, pay the guy and get the laptop back to his place while I went back to my place to get my half as I had some cash and meet him at his place since we both lived nearby.
When I arrived at his home 15 mins later expecting to see the latest laptop all I saw were two 1.5 liter Vanilla Coke bottles

. I asked where the laptop was and he said he made the exchange with the guy (who was sitting in the passenger seat) simultaneously, he took the laptop from one hand while paid with the other and they drove off and all he found in the laptop bad were two Coke bottles. Something which I found very unbelievable and stupid of him to do. I would have at least asked the guy to open the bag and show the laptop before paying.
To this day I don't know if the scammer was the white guy or my (former) friend. Either way it taught me a good life lesson.