Ok, to prove that I'm not totally alone and there is a problem with Flash, this page runs my computer and others CPU up to 100% usage and
WARNING: literally locks my PC until I close it:
http://www.lanik.us/misc/ff-flash-test.html
It's nothing more than a page with several embedded flash videos (check the simple source code),
none of them set to play. All they are doing is sitting there waiting to be played.
Any page with similar heavy flash content, video or no video, banners, adverts, widgets etc can cause the same effect. Each object uses excessive amounts of CPU.