I wondered how long it would take for people to start scamming Disney with that policy. I've been going since the late 90's, and the limits have always been $500, $1000, and $1500, and no hold taken at check-in for incidentals like some other places do (although they are able to see how much limit you have left at check-in - not sure how or whether that's a violation of some kind, but they can, I've experienced it).
Although I don't like the way other places do it either, with taking a hold for a predetermined amount X # of days, and then charging the actual charges at check out on top of that before the hold falls off.
But yea I guess I don't blame Disney for wanting to try to protect themselves a bit more. Up until now they had essentially been giving you a Disney World credit card of $500-1000-1500 at check-in that you didn't have to pay until it hit the limit or check-out day, whichever came first.