Can anyone quote the opt-in language that Microsoft uses for the Bing toolbar? Although I'm still not sure about whether there's a difference, I think there's a clear distinction between watching users of your site and taking action based on that (Google and search link clicks) and watching users of your toolbar everywhere on the internet and taking action based on that. (And that distinction is as clearly drawn between google.com and the Google toolbar.)
I've always felt that, yes, Google collects a lot of personal data, but they're up front about the collection and they give me good value in return - which is sadly not my general expectation of data collection.
It's clear that search engine use user 'feedback' to improve their search results.
But if
"Bing even sent Google synthetic and organic search terms, to analyze and make use of the results",
I would suggest they add 'powered by Google' to their search result page.
Further, I don't think it makes a difference if Bing is querying Google directly or using opt-in users to do so. In any case, their copying search results efforts from Google.
I have no issue whatsoever with Bing analyzing the data sent by opt-in users that is further processed to help increase its search relevancy results.
I would not care if Bing even sent Google synthetic and organic search terms directly, to analyze and make use of the results.
Remember, Google uses you (the searcher) as a product that is sold to the real customers: the adwords and adsense clients.
Google scans the net of content that they do not own, and makes an enormous amount of profit in return.
Google owns nothing. You owe Google nothing.