Earlier quoted context omitted.
You can get user-based statistics without cookies with: (new Image()).src="http://your.tld/track.png?ua=" + encodeURIComponent(navigator.userAgent); and then parse your logs. Update: this is just an example, as ars notes the user agent is sent as a HTTP header. But screen resolution etc is not.
Look, there are tons of data available in the browser, see http://panopticlick.eff.org/ for a good example. But they are non-stable for reasons outside of the user's control. So, if a user wants to kill her cookies every day, cool, they can. They can't randomly change their useragent+screen-resolution on a daily basis with the same ease. In addition, UA changes outside of user's control (a browser update pushed on th…
As for mechanisms, to what end, if nobody bothers to use them? Especially things like "randomize User-Agent string" that'd break a great many "non-evil" sites?