One troubling thing (for Bing users, that is) is that they took the info from the user-toolbar interaction, and incorporated it as is into bing's results. WITHOUT EVEN CHECKING THE PAGE! In their test, google did this:
They artificially made the search for the word "akjsdlfjalsdjf" (for example, i dont have the actual words) return the page xxx.yyy.com. The page itself has no mention or relevance to the search word.
After a few weeks it apeared in bing!!! WTF?
On a different note, to me it seems that if Google finds an obsecure page, Bing would learn about it from the user-toolbar interaction. kinda cheap in my book.