This was really freaking me out, so I called to verify what actually happens with your credit card.
And before I begin, I have to ask this in all seriousness....I've called WDW about 4 or 5 times now, be it a hotel, CRO, or merchandising, and without fail, I have been treated extremely rudely. Does this happen to anyone else? I'm always as polite as I can be, and without fail, I am treated like the stupidest person alive!!!! I'm really planning on sending a letter to WDW. Not an E-Mail, but an actual letter. I'm really sick of the shoddy treatment I get when I'm shelling out a LOT of money!
Anyway, I found out that the amounts people have listed are maximum "lines of credit" that can be opened. I was told that a hold is not placed, but rather a line of credit is opened. (I claim financial ignorance here, but the principle of both seems to be the same to me) The maximum you can request is $500 at the values, $1000 at the moderates, and $1500 at the deluxe. You can set any limit you'd like, or as someone else pointed out, you can simply not have charging privleges with your room key. They didn't say anything about not opening a new line of credit once you've hit your initial limit.