This is happening more and more. See forums on www.photo.net for examples.

The security fear is one angle. It's increasingly routine to hassle people for photographing things while standing on public property, and to impose photo bans where you can legally get away with it.

The fear of pedophiles is also behind some of this. A number of towns in the UK have banned _all_ photography in public parks and beaches, for fear that some pervert will get off on pictures he takes of kids playing.

There are also cases (though still rare, I think ) of American primary schools banning photo/video of school events like sports, plays, graduations, etc, for the same reason. Of course, such bans also have the effect of channelling business to the schools' official photographers -- schools with such bans usually contract with a pro and then sell copies to interested parents -- but that's clearly just an unintended side effect....