OK, out of curiosity I actually tried installing the Bing bar (on IE9 beta, which, btw, makes you manually activate add-ins after they're installed. The installer for the addin itself is pretty upfront about it sending your click data and stuff - it's right there on the one and only options page, next to one of three checkboxes - though the box is checked by default which I think is dubious).
I haven't been able to influence the Bing search results (no surprise there, since I've only spent a few minutes on it and not weeks like the Google folks) but one thing I did find very interesting was that if you search for something on another site, the Bing bar actually lights up and populates its own search field with your query so that with another click you can search for it on Bing.
As far as I can tell, the bar doesn't seem to be using any heuristic to tell what is a search query but just has a list of sites/URL patterns it knows about. Besides Google and Bing itself, these include Wikipedia, Yahoo, Ask.com, Amazon, Facebook, eBay, YouTube, MSDN and IMDB, but not Twitter or DuckDuckGo. This doesn't prove anything about how it's feeding search results of course but it does at least suggest that the Bing bar is very interested specifically in search queries, though not only on Google.
I haven't been able to influence the Bing search results (no surprise there, since I've only spent a few minutes on it and not weeks like the Google folks) but one thing I did find very interesting was that if you search for something on another site, the Bing bar actually lights up and populates its own search field with your query so that with another click you can search for it on Bing.
As far as I can tell, the bar doesn't seem to be using any heuristic to tell what is a search query but just has a list of sites/URL patterns it knows about. Besides Google and Bing itself, these include Wikipedia, Yahoo, Ask.com, Amazon, Facebook, eBay, YouTube, MSDN and IMDB, but not Twitter or DuckDuckGo. This doesn't prove anything about how it's feeding search results of course but it does at least suggest that the Bing bar is very interested specifically in search queries, though not only on Google.