Google recently became somewhat infamous when it became public knowledge that they are recording, storing, and analyzing every key stroke of their registered, logged-in users. Personally, I believe we can be fairly confident all (certainly all the big ones) online services are doing this to some extent. And the key words here are "registered" and "logged-in". If that is not your state then you have a chance to preserve some of your privacy.
The behavior to be avoided is the use of one provider for everything, for instance: Google Search, Gmail, GTalk, Google+, etc. Then you are giving that one provider, in this case Google, EVERYTHING. And because you are using all Google's services, you can be fairly sure that you are always logged into Google in all your browsers, even if you use multiple browsers. Even with the best intentions you will often forget to log out and remain logged in for perhaps days without even knowing it.
By "service provider diversification", I mean you should use different providers for different services. For instance, in my personal case, this is a simplified description of what I use daily:
That way Google gets ONLY my social media activity and some chat. Microsoft gets ONLY my search activity (and at that, I am faceless to them because I do not need to login to use a search engine) and some of my chat. And gmx.com gets ONLY my private e-mail (actually, only some of it, because I also run my own e-mail server, which is even better -- all geeks should do this).
"Your browser fingerprint appears to be unique among the 1,433,795 tested so far."
I thought I was just running NoScript to protect myself against hackers, but now I am more then doubly motivated to continue to do so.