I have to say, when I see these posts, I think people are looking at this the wrong way. The vast majority of US hotels would never let 5 people stay in one regular room. Heck, many of them won't even allow 4. Disney not only allows it, but has several room configurations to ensure that families of 5 are able to sleep comfortably. They are unable to guarantee a particular room configuration for a family of five, but they do their best to meet guest requests. They tell you that up front - yes, you can have 5 people in a room, and yes, we have rooms that sleep five, but we cannot guarantee you will get one. (Therefore, if one books a room anyway, I hardly see how one can be upset if the requested room is unavailable.) And then, if it is not possible for them to honor the particular room request, they are kind enough to offer a sleeping bag for the 5th guest to be a little more comfortable. They could easily say, "too bad, so sad" the way some hotels would.
Just my .02.