Some people (like me) just don't mind. Tracking is not inherently bad, and they use that data to provide some value for users. If you had to inform everyone and provide opt-ins for every single feature that someone out there might not like, nothing would ever be done on the Internet.
Also, running analysis on this kind of data must be pure awesomeness, from scientist's point of view ;).
You'll note that I made no statement regarding the goodness or the badness of tracking. I merely stated that Googles business model relies on the majority of people not being aware of the tracking, or not caring enough to disable it.
Also, running analysis on this kind of data must be pure awesomeness, from scientist's point of view ;).