Does Disney World allow overbooking their restaurants?

I read in "Walt Disney World with kids 2007" that you should over book your meals and then you can cancel reservations when you figure out where you are going to eat. I would like to have a dinner option in each park each day so that we are not tied down to a schedule. Like if we're having a blast in Magic Kingdom we don't want to have to rush to Epcot just to make it to dinner. Can you call in multiple reservations or do you have to be somewhat sneaky about it and make several calls?