if you dont need flash dont install it. you can view youtube videos with totem, miro, moovida, or various download scripts.
lots of sites have a flash and an html version. even if you use flashblock, it reports to the site that you have flash installed, so you get the flash version. if you remove flash you get the html version.
i installed flash into firefox in a second user account. on rare occasions that i want to browse with flash i use use ssh to start firefox as the other user.