Ebay 有 Money back guaranty. The risk is unlikely due to buying/selling, it is more toward to how secure Ebay is capable of keeping all his customer's sensitive information. All banks have the same issue. The only thing you can do to protect this is to purchase credit card insurance and identity theft protection, which are expensive.
However, Paypal will become independent this summer (may be a good buy for its stocks!), which will impact how Ebay refund his customers.
I'll post a recent experience with Ebay which I got my money back due to a lost registered mail (flying geese cover). .