I don’t like Google aggregating this data about me. It is possible to opt out. You can turn off search history recording in the settings page. You can also edit your history, including removing it entirely.
It’s still unclear to me exactly when Google started recording these histories under account names. Six tech savvy friends I asked all found they had some sort of history on Google going back as far as eighteen months. Only half of them remember having turned on some personalization feature that would have resulted in that history being collected. A seventh friend who is scrupulous about cookies and logins had no history. He regrets that his privacy concerns keep him from using Google Reader.