Disney does have a problem with (typically teenage) chronic
> troublemakers. They get caught, given the usual don't come back on
> the property spiel, and escorted off the property. The problem is
> that some of them come back with revenge in mind. By getting these
> folks prints and scanning everyone upon entrance, they can easily
> recognize them at the gate and block them.
While I don't doubt that is one use of the technology, I'd have to see the details of the implementation before I'd believe that the hand geometry from two fingers would be sufficient to uniquely identify anyone.
What is far more likely in my mind is Disney's ongoing desire to prevent multiday passes and resort passes from being used by more than one individual. I suspect that Disney ties a hash function of a few points from the hand to the serial number of the pass.
Try to use the pass by someone else and the odds of the hash being the same are sufficiently high enough to be detected ...