I agree that the intention with the reservation makes a difference.
But how can you, I, Disney or anyone else for that matter decide what my or anyone’s else intentions are with a specific reservation?
Because they are allowed to in the contracts we signed. A lot of things are decided "at the discretion" of
DVC...
There are plenty of things they could to combat the problem. Some would have to assume the members intent at some point, yes, and some would not.
A series of coincidences clearly becomes less likely each subsequent time it happens. DVC could simply look at a member's reservation history and using other context clues, decide if it looks suspicious or not. This would of course require assuming intent at some point, which they are allowed to per the contracts.
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Ex. When a long time member who usually uses the bulk of their points rents out a single cheap studio in early December, they would of course get the benefit of the doubt.
But when a fairly new member who has used all of their points for the last 3 years to book 10 studios in the most popular time of the year in the cheapest studios, and has never stayed in one of them and has rented them out, then obviously that member may be more likely to be considered to be renting commercially and breaking the rules whereas the first member was not. They have to look at more than the individual booking itself to get answers.
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Then they could do other things that do not require assuming members intents, but that would affect all reservations. Things like enforcing the verbiage that guests names should be on the reservation (and that members services should be alerted that a guest is a renter) at the time the reservation is made. This would potentially stop lead guest name changes on confirmed reservations to anyone but verified family/friends, and would make the system much less flexible. That is why I would do something else to increase flexibility at the same time if I were DVC and were going to do something like that.
For example they could do something like allow refunding of borrowed points or banking of points past the deadline once per year as part of a reservation cancellation to compensate for this. A normal member would not usually be upset if they for some reason had to cancel a reservation but they were able to bank/refund the points for future use or even to be able to rent out in the future on a non-confirmed reservation. A commercial renting member would probably be upset however.
ETA: They could also simply add more things that members can sink their points into (or give better value for, allow holding points to be used for, etc) instead of having to rent them out. They started doing annual passes recently in addition to cruises, interval international, world collection, etc. Give members more good options or better value for their points and they may not have to/want to rent out points as often.