I personally track people by server side scripts only. Like the IP, browser they're using. Usually is enough to track individuals.
Where someone is from can be found with the IP, (Geolocation) and the redirection link from Google or Bing(or any search engine) is sent from the client as a header.
I only plant a cookie on the users system to identify who they are. Just a single session cookie required for the site to be operational. Then tie everything I have over the user to his session cookie, ip and browser. So far this seems to work very well.
And because my country requires websites to ask people to accept storing any non site-operational required cookies. And the EU will soon follow with this legislation. My country alone can't do anything to foreign webhosts. But the big players are already giving in to my little country(MS, amazon, etc. Google and Apple don't ... yet). And the EU will have more power behind it
Saves me bugging people with "HEY DO YOU WANT ME AND THE REST OF THE INTERNET TO TRACK YOU?!?" or not do so and risk legal issues.
EDIT: I tried the https://panopticlick.eff.org/
It requires Java (don't like that) but I allowed it. Stops loading on IE10 desktop, or rather it loads forever.
IE10 metro however
Currently, we estimate that your browser has a fingerprint that conveys at least 21.38 bits of identifying information.