To track even a few
searches, however, would require some form of cookie to be served to a user--the foundation for behavioral targeting at its simplest. "Obtaining the latest query does not require cookies to be
assigned and tracked for that search," Schwartz says. "But to track a query from five searches ago, you will need to assign a cookie to that searcher and track his queries. Then Google can use that
'cookied' data to tailor the ads from a query done several searches ago."