Disney in general would lose a small fortune if they strictly enforced the four person rule across their various resorts. Some families would trade up to a larger room or book two rooms, but thousands every year would stay elsewhere, making them more likely to visit Universal/SeaWorld etc.. Many of the other trickle down expeditures that go along with a vacation would be spent elsewhere as well.
DVC is a different story as the members are the owners and have a direct interest in the wear and tear on the facilities. But from Disney's standpoint I don't think they will ever care enough about that to enforce the four person rule, certainly not in a one-bedroom, especially when the extra person is a child.
Why do they have the rule then? I'm sure they've done every statistical study imaginable to make sure that whatever the policy is, it maximizes the bottom line. They ultimately compute the balance between profit and guest comfort... how crowded is the pool, how long a wait for an elevator, how many rings before housekeeping picks up the phone, THEY STUDY EVERYTHING! They compute an optimim number of guests that can be accommodated and average it amongst the number of rooms.
If they set the rule at four and enforce it, they would probably be below the <b>optimum</b> number of guests. But setting the rule at five, or not having a rule, might be too much (maybe inviting people to squeeze six). So they came up with a compromise that matched their statistics.
Let me put it this way, I would be willing to take the following wager. If Disney was made to stricly enforce (without any exception) an occupancy limit at DVC resorts, that limit would not be four to a studio/one bedroom, not in a million years. I invite anyone to survey their DVC guide with the following question. How would they like to pitch their prospect (family of five) four nights in a two bedroom off-season in place of their two week vacation at an on-sight Moderate (oh, and by the way you actually get to stay on the weekend once every four years!)? How would Disney like having that family spending four days a year instead of ten+ days a year at their theme parks, restaurants, gift shops, golf courses, night clubs, etc.? I don't think they would save enough on the re-fillable mugs to make up the difference

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So, are you breaking the rules? My answer is that it is a matter of semantics. There are laws and rules and guidlines and suggestions and recommendations. My advice is to tell Disney the truth at all times and do exactly as they say. If they tell enough people that the rule is four and there are no exceptions (if they do this and you sneak in five you are most definitely breaking the rules), they are going to have to change their marketing of the club significantly, and the resorts will take much longer to sell out. The fact that Disney even offers financing is a red flag that they are not marketing this thing to people who can matter-of-factly afford to stay five to a two bedroom [BTW, do the ladies maid and valet get their own studio in this case? What about the nanny and chef?

]. If enough well-to-do DVCers are put off by the number of guests staying in a particular room, they may be successful in pressuring Disney into strictly enforcing an occupancy limit (turning the psuedo-rule/guideline into an actual rule, some might say). But they shouldn't be surprised when that limit turns out to be five to a studio and six to a one bedroom, that's all.
John