An interesting new twist on things, rather than using cookies to store information you can use perpetually cached files.
So clearing your cache and cookies isn’t enough, could be a privacy issue you say, indeed it could..
You can view a live demo here.
This is a demonstration of how a person’s web-browser can be tagged and tracked using a unique identifier which lives in the web browser’s cache for a very long time (using HTTP cache control headers and browsers’ use of conditional GET requests). This serves the same purpose as using a cookie to track people. However popular web browsers lack finer cache disposal controls (compared to cookie disposal), and this is something which needs to be looked into. No private information is collected in this example. It has been tested on Firefox, IE6, Konqueror and Epiphany. I don’t know about the IE7 versions or Safari.