Just to put the alternative point of view....
I've had a few bad experiences in the past on e-bay with buying poor quality goods, but at the prices I paid, I couldn't really complain.
A few weeks ago, I bought a 16Gb USB memory stick. When it arrived, it was only 2Gb, hacked to look like 16Gb. After studying the feedback, it seems the supplier was an out and out rogue, rather than just a supplier of crap, so I contacted Paypal and went through the issue resolution centre. Had to be a little patient, but in the end, they paid my money back, kicked him off e-bay and left me with a 2Gb memory stick for free.
Now I realise this was a low value transaction, and easier for them to just pay me off than spending time investigating, but it shows that it can work
Thumbs up to Paypal on my example