How much Google knows about you?

I’ve read just now an excellent post about the ways Google is gathering data about you, about us. And if you  think about you came to realize that indeed the amount of data Google knows about you is scaring. Even for me, a Google fan. They know what you searched, what you bought, what sites you visit, what are your preferences and so on. We came to the point where Google has more knowledge about an individual then any other entity in the history of the world.

I have faith that Google as a company will not misuse this data. But what about a security breach ? No matter how secure you think you are, there were always ways to compromise that security. And this can happen to Google too. One angry employee, one little security breach and this data can fall into the hands of people not so benevolent. And i didn’t said anything yet about governements who can force Google by law to hand out this data to them. 

These questions need answers and actions. We will have to change our behavior and restrict the data we provide to such companies as Google. But how can we do that ? Can we do that ?