Kodak's current stance, which seems to indicated that there may in fact be higher exposure scanners in use for some hand carryons! http://motion.kodak.com/motion/Suppo...ys_airport.htm
"Carry-on baggage inspection conveyors using low intensity x-rays, used at security checkpoints in US airports, usually do not affect film. However, these machines may now be supplemented in some cases by high intensity machines that will fog all unprocessed film. Travelers should be wary of all scanners at foreign airports."