I'm quoting Bizaro86 from the wmowners forum. This idea could work:
"I think a combination of two changes would suffice. Randomize the time until cancelled reservations come back.
Make the waitlist of no effect until 12 months, but let owners submit waitlists between 12-13 months, and then put the list in random order.
That would kill cancel and re-book, because people wouldn't know when to look for their bookings to pop back up, and couldn't be sure they were first on the waitlist."
This should stop megarenters and people managing other people's accounts. It doesn't change the flexibity of the system for owners - they can still waitlist, they can still make the reservations they currently are allowed to make. People could still make long reservations. The "black hole of cancelled reservations" helps, but I think people who have working the reservation system as a full time job would figure something out... They could check online continually for their cancelled reservations to show back up, and grab them as they reappear. It would be much more work than is currently needed, but still possible. It would get rid of "reserve 10 days, cancel the last three, rebook a new 10 day reservation."
The rebooking issue is what irks me most. It's frustrating watching the units for the day(s) just past 13 months disappear throughout the day at 13 months.