Turn off your cookies or use in private browsing.
Done deal.
Don't you believe it. Google pref cookies are not enbedded in browsers like Firefox and others. Google has paid them to make it where you can't get rid of the cookie. It does not show up in the regular cookie folder and even if you dig it out it reloads with restart of your browser.
http://blogs.wsj.com/digits/2012/02/28/the-google-cookie-that-seems-to-come-out-of-nowhere/