Paranoid Privacy Parts
Get over it. Really. Let them track you. So they know that you visited Walmart and then Blockbuster and then Gmail. Yes, Google knows a bit more and there is more risk. Google actually knows who you and I are when we are doing something. So they know where I live, who I email and what sites I visit and when. They even know what I've searched for and could theoretically mail me ads for things I've searched for to my home address.
And yet, I like that they know this about me. I WANT them to know this about me. The ads they serve me are more relevant because of the information they have on me. I now see ads when I visit other websites that are relevant to me. For example, I see ads for pampers instead of Depends. Fortunately, we are almost out of the pampers stage. (Oops, there I go again, ignoring my right to privacy).
Yes, there is risk in Google and others knowing too much. Perhaps you were mortified by the story of Target being able to track when a woman is pregnant without her knowledge. The most ironic part of the story is how Target new before the father did. But the secret you need to pay attention to is that it had nothing to do with her online behavior.
I liken the current privacy scare to 10 years ago when people didn't want to use their credit card on line. Better to put your credit card into the internet 10 years ago than it was (or is) to give it to waiter/waitress who can easily copy down all the important information.
We need to be smart about what we worry about and focus on the things that matter. There is value to sharing this information, so share away. Yes, some day this may be used against us. I'm not saying to ignore it, just not to overreact. Keep an eye on it but realize that right now, your secret is safe with G...
If you want something to worry about, worry about these killer robots.