"[W]hen we authenticate ourselves with Google, Yahoo, Verisign or whoever our Identity Provider of choice is, that website will pass a different, unique URL to

"[W]hen we authenticate ourselves with Google, Yahoo, Verisign or whoever our Identity Provider of choice is, that website will pass a different, unique URL to the government site we're logging in to." Sounds like Google, Yahoo, Verisign or whoever [sic] will have a lot of information about which government agencies you interact with and how often.