http://news.bbc.co.uk/1/hi/technology/6692063.stmGoogle collects and stores data from each query. It holds information such as the search term itself, the unique address of the PC being used, known as the IP address, and details of how a user makes searches, such as the browser used and previous queries to Google.
That information can contain private data about a user, and could be used to build a detailed picture of the user's habits or lifestyle.
Google knows all