I'm sure the thinking here was:
1 - since he's a celebrity and well-known, he wouldn't pose the same kind of threat as an unknown "wild card" that any other passenger could be.
And, probably more importantly for Disney,
2 - the photo op, publicity, and possible extra revenue was worth "bending the rules for."
In my opinion, Disney missed the boat (no pun intended) in two ways here. First, I'm sure Mr Carter wasn't unaccompanied on his bridge tour. From what I've seen, there seems to be a complete entourage of people that would follow him around...any one of which could be a "wild card." And secondly, Disney failed to take into account that its customers *would* in fact be annoyed that they seem to put "the rules" (not to mention the safety of every other passenger on the ship) aside in order to accommadate a celebrity.
Poor showing, Mr Eisner.
Julie