Just to clarify: if a school decides to DENY your application and you HAVE had an interview already with that school, then there is a 99% chance you will NOT hear anything until Dec. 1.
Those who are getting rejections PRIOR to Dec 1 are just that -- rejections of their applications, not denial into the school.
The reason for this is that if you were good enough to get an interview, then schools will NOT just outright deny you, they will typically sit on your file and see how many of the people they gave acceptances to will pay the deposit. If they get enough people promising to matriculate, then the schools have no need to dig into their "waitlist".
So, to sum, it is fairly rare for schools to deny you (if you've had an interview) on Dec. 1. Usually they will string you along until they get their class numbers just right. Sometimes this entails giving YOU an acceptance, other times it just entails them keeping you in their back pocket in case they need you one day in February or March.
For example, I interviewed at UNLV in October of last year. On Dec. 1 I called them and was told that I was not accepted on the initial round of acceptances. I called them in January and was told I was not accepted in that round of acceptances. Still, I had not been denied and my file was still open. I called them in February to let them know I had chosen Arizona, but before I could get that out they told me I was accepted.
Contrast that with my application to Iowa, where I was REJECTED prior to secondary, or UK where I was REJECTED prior to interview.
Make sense?