http://www.google.com/policies/privacy/preview/
Starting on March 1st, Google will have a new private policy in affect. Google's new policy is different from the old policy by allowing users to restrict some things from Google from recording and using their information.
To restrict Google from containing certain information, you can use the company’s services without signing in to your account(Gmail). This can restrict Google from collecting information on you. If you are always in your Google account, the person with the account can turn off the setting that allows Google to record their search history. Google will still keep some of your web history but this new policy will allow you to have some control over your web history among other things. I think this new policy gives users some control on their web history, but not full control. All I can say is that be careful on what you type in that search box. Also if you do not know what Google Dashboard is, it offers users a view of your data related to your account. The dashboard also gives you control of your personal settings such as your personal information. It also allows you to have an email, maps, document and many more. That is something you learned if you didn't know that.