The particular code that we are speaking of here is a code that came out in January. It was for particular dates throughout the year. You can do a search on the "40% discount" and find the associated threads.
No one knows for sure, but most people think that this code was meant to be a PIN code, which means that you would have to have a PIN number associated with your name in the Disney system to get the discount and you probably received either a postcard or email telling you about the discount. However, their was some type of "glitch" (or lack of training!) that allowed the CM's to give this code to people who did not have a PIN associated with their name (I was one of them). There has been much speculation regarding what will happen to the reservations of the people who received this code without a PIN, but so far, no one that we know of has been contacted about their reservation and told that they would have to pay rack rate. However, Disney has really cracked down on people using this code who do not have a PIN. But, you could always call Disney and ask if you have any codes assoicated with your name. It doesn't hurt to try!