All things being equal, we can assume that Amazon will fair a better chance of competing with eBay because their core competency fits squarely in the retail space and auctioneering is a logical extension. Amazon customers equally have a greater degree of trust with the brand than Yahoo customers for the kinds of leaps of faith that auction retailers require. So, Yahoo and Google will have to work much harder than Amazon to compete with eBay, but this does not rule them out.

It’s also worth considering any new entrants into the space, but the network effect will pose a tremendous barrier to the market. While the internet greatly reduces this barrier, awareness building and trust still need to be built the old fashioned way.

Another interesting question to consider is whether the online auctioneer will be able to make use of the LONG TAIL phenomenon: the ability to coordinate auction items with each other. For example, if you buy a set of turn-tables, will the auction site offer you LPs as well? The kinds of obscure product listings lend themselves well to take advantage of the long tail. But the complexities of matching products and classifications will be a big challenge for the retailer. 

More importantly. In a developing e-commerce nation such as China, where trust of online financial transactions is shaky at best, all it would take is one giant scandal to hit the papers and get carried to everyone. Such a disaster would likely taint eBay for years in a nation already wary of corruption and con men.  

Please do not over-rationalize branding as this leads only to misconception of what branding really is. Those greatest competitors are good to keep the industry to guidelines, to make it more competitive, but eBay (also owner of Pay Pal) seems to be and to stay the leader in on-line one-to-one interactive sales in nearest future.