If you log in and then back out, does Google still have a record of which user was on which IP and use that info though? (I can't find an answer)
Couple of other things that spring to mind is Virgins Advanced Search service (that you had/have to opt out of). If you mistyped a URL, Virgins DNS servers would step in and offer you some 'suggestions'.
That was a bit too suss for me.
And there was the AOL fiasco a few years ago where the ISP kept a record of all their account holders searches conducted through their own internet search service...that were subsequently leaked.
http://en.wikipedia.org/wiki/AOL_search_data_leakI suppose the only way to make it difficult for them is to use a VPN Proxy service.
