they cant really take people's phones... so they can't really enforce it...
I'm the same as you... it's cool to take a footprint (This happened), so you can go back and relive, remember... but if you forget to be there... then you stole the experience from yourself.
I was watching a documentary about King Crimson. They have people at their shows who will tell fans to stop filming. They put up signs at the start about this and say photos are allowed once the show has finished and they take their bows. Other bands don't seem to mind so much.