as i waited in line, i was warned over and over again that no cameras were allowed in the sistine chapel. so by the time we made it in there i was resigned to keep my camera off and to instead, buy the postcard on the way out. but once inside, after the initial sensory overload of seeing Michelangelo's amazing masterpiece, now restored to its' original brilliance, i became aware of the sheer number of people who were holding point and shoot cameras over their heads and firing away. and with the flash on no less! every time a flash went off you'd hear someone call out in an official tone, "NO PICTURES!". but that was it -- no other repercussions. when i visited the National Archives in Washington DC a year or two ago, the guards there were a bit more serious in their roll, confiscating cameras and physically removing anyone who violated their rules. but not in the sistine chapel.
eventually i figured out that if i knelt down behind the crowd at the far end of the room, that i could take as many non-flash shots as i wanted, without interference. thank goodness for L series lenses with image stabilization! :)