Ebay is a service provider that provide a single access to what's sold by many. Problem is there's little control over individuals that sell things. There are companies that are unreliable but individuals can be total unknowns. I always recommend that when you make purchases on the web they should be from reputable companies that you can verify. I feel safe buying SD cards and many other computer items from Tigerdirect and Newegg. The prices are competitive and they have a long history of being in business.