Doesn't this achieve the exact same purpose as logging a combination of the user's IP address + user-agent + maybe some other stuff? Don't need no complicated, cunning technology to do this...
Exactly. On http://panopticlick.eff.org/ you can see how 'unique' your browser configuration, ip address, language settings, etc are. For most people, this creates a great many bits of information that can be used to track you even without cookies or any client-side storage.