I'm flying rotary in and out of Royal Ascot all this week and we often buy pics from the spotters to use in advertising, there are some remarkably skilled snappers out there doing it for a hobby. I've also found myself in the same situation as ShyTorque, usually I tell them to snap all they want but to please respect the privacy of the pax and neither approach them or photograph them, I've never had that request refused.
It does amaze me when I'm on the jet just how much info they have about our movements, if the Olympic Security people for London knew what info is out there they would probably shut down all UK airspace for ever!
SND