I doubt the debate would get this nuanced, but I believe Google only tracks users on their own site. It appears Microsoft is tracking click across at least one search engine.
I think this distinction has legal as well as technical implications.
I think this distinction has legal as well as technical implications.
* all with some specific exceptions for perhaps SSL and locally-resolved zones, or something like that.
The big search engines are large enough to show up clearly in any of their competitors statistics (and there are always human teams monitoring the automated process) and should specifically exclude data from their competitors.
For Google to use Bing clickstream or vice versa also perpetuates a vicious circle where bad results from one search engines will spread among the others.
Bing either hasn't acted ethically, or hasn't though through the consequences of absorbing clickstreams of competitors' sites.