There are many other techniques employed. As soon as one of the techniques works, it re-populates the others. (Cache clearing doesn't affect Flash cookies [LSO's]).
This is coming soon to a Chrome near you: http://blog.chromium.org/2011/04/providing-transparency-and-...
Presumably other browsers will follow.
http://blog.sidstamm.com/2011/05/clearing-flash-cookies-usin...