Even though I like Google, I am not comfortable about the fact that it maintains tracking information for all searches, for an indefinite time. A few months ago, AOL users' search data was compromised. Even though Google might be more diligent about protecting their users' data, there is always a threat that it can be forced to share the data through a government subpoena.
Did you know that Google stores a unique identifier in a cookie on your PC, which allows them to track the keywords you search for? They use this information to compile reports, track user habits, and test features. In the future, it is possible they could even sell this information or share it with others...
well.....