I try to stay out of heated topics, but I am going to add some information to the discussion of holding multiple DISCOUNTED reservations...
When I worked in reservations at a large hotel chain, our discounted rooms did not go back into the pool with the discounts, but rather to rack rate. If Disney does the same, if you book more than one discounted room while you decide where you want to stay, the room you cancel will no longer be available with a discount. I have a friend holding AKL and All Star reservations for the same dates, I didn't bother going into it with her.
I'm not sure why it would matter if you have a non-discounted reservation and then book with FD before you cancel the first? I waited to book my room until FD was announced (more rooms booked = less rooms put into the discount pool), but we just decided to go a few weeks ago so I knew to wait to make my reservation.