In a interview with FT ebay CEO Meg Whitman claimed "The four dominant internet groups - Google, Yahoo, eBay and Amazon - will increasingly focus on their core activities rather than compete with each other head-on...I think we will end up specialising,...We have specialised in e-commerce, payment and voice communication. Google stands for search, Yahoo largely stands for content - so I think we may on the fringe compete, but I suspect that over time the businesses will become more specialised."
That sounds reasonable, or is it!?!
The more obvious differences are in the revenue models, broadly: Advertising for Google, Ads & paid content/services for Yahoo, commissions for ebay and sales minus costs for Amazon. All these require more than a few geeks working on Ajax, it means different competencies, capabilities, supply chains, distribution, business relationships, alliances and so specializing and focus will definitely help in ensuring efficiency in operations.
Inspite of all efficiencies, effectiveness & strategy will only be driven by two things 1. User Experience 2. Communities, and that is where the differences begin to collapse and all four do begin to look like competition.
Another way to look at it would be that a user reads about the newest, coolest widget on Yahoo, researches about it on Google, while clicking on a few ads there, buys the product on Amazon, and then auctions it off on ebay. I guess it would be easiest for ebay to move upstream, scale up and/or out spanning the entire chain and even into all aspects of e-commerce in manner that significantly impacts even mainstream retailers/manufacturers forcing them to set-up shop on ebay-ville(ebay-halli in Bangalore). I also do feel ebay has the maximum stickiness, durability & network externalities among its community compared to the other three.
It truely is a drama of epic proportions being played on the most exciting theatre: Internet