> searches on Amazon and Ebay and others should also be included in any assessment of search market share

Thanks, this is an interesting point. Search users fit into different profiles based on context. Marketers have known this for a while, as different keywords target users in research mode, ready-to-purchase mode, review mode, etc. Buyers searching for "best blue widgets" have different intent than "cheap blue widgets" or "buy Acme blue widgets".

Specific engines like Yelp, ebay, Amazon target users in specific contexts, but google targets general contexts. Why should Google avoid improving searches for specific queries if it has the technical ability to do so?

I suppose the question is, did Google overstep boundaries in the way it improved search results for specific contexts? Did Google violate antitrust laws by scraping content from these context-specific engines, then effectively saying "if you don't like it, we'll stop, but you can't use our search engine" (Yelp). [0]

[0] http://bit.ly/1ILbpMb (non-paywalled WSJ article via Google search, ironically enough)