http://googlesystem.blogspot.com/2007/04/how-to-disable-google-personalized.html

It's an ongoing topic*, but the Depersonalizer was new to me...

* http://blogoscoped.com/archive/2007-01-16-n41.html

If they're respecting the "pws=0" param, you can add it to the search bar in Firefox – crack open the "google.xml" definition from the SearchPlugins" dir, add "Param name="pws" value="0"", bounded by open and close signs, save and restart Fx.