As for google data mining: By using gmail I can't keep my mail away from google, but I can prevent them from matching the mail to other things. I don't do my google searches from the browser which is currently logged in to gmail, I search with another browser (e.g. konqueror - due to firefox' insistence on using the same browser even when you try to start another one). And cookies are all handled as session cookies of course. And IP addresses are not matched either, or not usefully at least, because it's NAT'ed together with a huge group of people.