As a frequent flyer and aircraft enthusiast I snap along during most flights (exception being night flights).
Occasionally I have had an FA attempt to forbid me (never on CO though).
As no law forbids it I usually ask him/her to provide me with/quote the law that outlaws such practices :-)
If the "no electronics" rule is invoked, hey presto ! I whip out the letter I got from Canon stating that my cameras are flightsafe.
Up to now no more hassle was given after the latter were mentioned :-)
UTA