I've recently found this news on Wired about a USA lawsuit against some major USA websites that seems to use Flash cookies to re-set browser's cookies (the standard cookies we are all familiar with). I think the name "zombie" cookies gives a very good idea about the practice.
My 2 cents is that re-setting browser's cookie using flash cookies goes against an explicit intention that the user manifested when deleting the browser's cookie and therefore this technical ability should simply not be used.
Having the technology to do something doesn't automatically mean you have to use it..
