Obviously, eBay is the big dog in the online selling market. Other venues also exist (Amazon, Etsy, etc.). While certainly not impossible, it won't be easy for a new player to break into this market and have a significant impact. It is important to remember that the marketplace is highly dynamic. Success by a new competitor virtually guarantees a response from the other players. This might take the form of policy changes to be more attractive to sellers, high dollar marketing campaigns to attract new sellers, and who knows what else. I applaud anyone wishing to give it a go.