Well plenty of people already take their cameras in.
Same also applies to all stadiums, yet the stewards still allow people to take pics.
What its really aimed at is people turning up with SLR cameras with 50x zoom lenses.
People with these types of cameras could then take unlicensed professional photos which they then sell on for profit. Therefore denying the legitimate photographers of their incomes.
A fan taking happy snaps with their friends on a basic camera or mobile phone isnt going to cause much bother.
granted some stewards can be a bit y about it, all i would do is move to a different part of the ground away from the jobsworth and then take the photo.