In 16 years of buying items on ebay, I've never really had any problems, and I've purchased everything from car parts, to plants, to thousands of dollars in jewelry to just about everything in between. The one time in 16 years I had an issue with a vendor, my credit card company reimbursed me.
eBay is probably one of the better places to buy from, since vendors live and die by their feedback, and there are multiple levels of buyer protection, ranging from eBay itself, to paypal, to your credit card company.
You do have to use some common sense though. If you see a vendor with a feedback score of 3 selling a high demand item for 1/3 the normal cost, it's probably not worth taking a chance. You can usually vet the too-good-to-be-trues by asking a question or two. The fly-by-night vendors will either not respond, or if they do, it's heavily broken English.
And when buying designer perfume at eBay, Amazon, or any other online store other than an authorized vendor (eg, macy's), there is a high probability of getting a fake.
