This debate always goes the same way. It's the same as the walking reservations debate, and they entangle themselves together frequently. It likely harms membership as a whole to allow the practice, but it's impossible/illegal/illogical to attempt to curtail it. Someone is going to ask how it harms membership, so I'll preempt you. Walking reservations and booking hard to get holiday reservations with the sole intention of resale puts stress on a system that it wasn't designed for. It's not an issue when a few people do it, but when it becomes as commonplace as it is right now, it breaks the system down. It's like putting your kid on your shoulder at fireworks time. It isn't against any rule, and if only a few people do it, only the few behind them will be affected. If everyone did it, it'd really suck for the short people. All I see is people arguing "it's allowed". That's never been a good excuse for anything.
Does it really break the system? If a time period is popular, the easy way to make it less popular is for DVC to raise the point totals. This benefits people who travel in other period of times as the people want the "popular" times will subsidize the less popular times. Repeat as needed when there's an imbalance. At high enough point totals, people who rent points won't find renters. People will then flock to the less popular times with less points. This reduces competition for the previously popular times. It also makes it less profitable for the owner renting out points as the person will have to commit more capital onto the gamble that the reservation will rent at that high of a price.