In the process of looking for a deal on eBay, I detected numerous problems on listings of various products (i.e: digital cameras and USB flash storage). I reported my findings to the Spanish branch of eBay but to date, four days later, I've got no answer from them. I did the same thing to eBay.com Safe Harbor and I've got an automated reply, but some hours later I could see that some of the users accounts had been cancelled.
After searching a bit on the 'net I can see that a common scam is to sell fake flash storage (either USB or SD or any other format). The trick is that the storage actually works, but it only contains a small amount of the listed capacity. Users buy the unit and after the initial tests it seems to work ok. The units report the fake capacity to the operating system, though after the user stores files that exceed the real capacity (not the reported one) all stored data is corrupted. Depending on the case the seller might be already missing or he may claim you've got a defective unit. Beware if you see a "too good to be true" deal on these devices.
How to spot a potential scam? To be honest I have to tell you that eBay does a good job about writing clear and straightforward guidelines on this. However, users sometimes might not have read it. The most clear sign that should put you in defensive mode is when seller ask for a wire transfer for payment. Next, you need to pay attention to the seller's feedback, not only on the number of feedbacks he's got but also if they were coming from sellers or buyers. Does he often sell the type of goods you are planning to buy from him now?
On the other hand, be also aware that accounts might be hijacked, so a crook could be using the account of another, decent eBay user, so look for sings reassuring you this is not the case.
But on top of that bear in mind you can always walk away. I guess you rather prefer negative feedback from a dishonest seller instead of losing some hundreds of your hard-earned money.
I think you can find good deals on eBay, you can also find items not available on your own country too. But be aware that products shipped from another country might have an import tax only the buyer is aware of.
I've bought a few items on eBay and I've bitten the dust once (DOA wireless router). I was naive enough to believe the seller was trying to help me out to fix the problem while he was just gaining some time so I could not file a complaint on time. After that time passed I've never heard from him anymore. Does anyone need a nice door-stop?
Update: Five days later, eBay Spain sent me an email telling me that as my user account was registered as US resident then I better should talk to eBay.com. No mention to the ongoing scam operation I was warning them about. They seem to care more about following the company's rules than preventing fraud. At any rate, five days is quite a large reaction time (It took less time for my camera to be shipped from Hong Kong).