… is the goal of this Public Citizen report, worth a read.
This excerpt from the introduction gives a flavor:
As Google has continued to flourish, it has become ever bolder and more sophisticated in its methods to collect and combine information about individuals to generate revenue. Most Google users are likely aware that Google collects information about them, such as their Internet surfing practices. Few are likely aware of the extent or sophistication of the company’s information-collection methods. Even privacy experts interviewed for this project said that they did not know the totality of information Google collects or how it uses it.