Furthermore, based on a quick estimate based on my current Firefox cookies, Google is (through Google Analytics) aware of 80%-90% of my browsing activity.
But the cookie is per analytics domain, right? And not directly linked to other google cookies.
So I think Analytics "sees" 80% of your browsing but it's multiple fragments, each going to different analytics domains. It's never seen as a single user.
Hmm. Thanks for your help; I'm sorry if I'm not understanding.
Can't Google make certain (admittedly imperfect) inferences based on seeing the same IP address visit gmail.com, then AllThingsD.com, then CA.gov, etc? (All of which use Google Analytics) It doesn't take rocket science to place a high probability that the the IP address that visited gmail is also me across all those domains.
It's not because something is technically possible that it should (or can) be done.
Why go through all the pain of setting analytics such that: it uses per analytics domain first party cookie, serves the javascript and the tracking gif on google-analytics.com (no google.com cookies are transmitted), but they would then try to reconstruct user behaviour based on IPs?
That would be quite deceptive (and might not allowed by the FTC and the privacy policy).
And they can already do global tracking with the doubleclick cookie. But it is explicitly not allowed to link it with other data without consent.
Edit: by the way, thanks for your questions, I never really digged into this and also at first assumed they would have access to a lot more information. But analytics is actually pretty well designed.
