I used to think this way, but these examples are still invalid. What would you say to an airline if you couldn't make the flight? Sure, they'd let you reschedule, but it would cost you.
I haven't flown for many years (and don't plan to) so I don't know much about the airline policies other than what I have read here on the DIS but I think the difference (IMO) would be the reason behind the policy.
I'm sure the reason for the airlines policy is money or the loss of it. I'm sure if they allowed anyone to cancel or change their flight at anytime for any reason, they would have trouble filling some of those seats at the last minute and lose money.
I doubt Disney is losing money due to last minute cancellations or those who just don't show up. I have read many posts here about ppl being turned away from restaurants because they weren't accepting walk-ups. Right now they are obviously able to fill the open tables so they are not losing money. If we had been discussing a policy change because of Disney losing money, it would be different. I know Disney is in the business to make money so I would understand if they changed their policy for financial reasons but in this case, we were discussing a change in policy to prevent double bookings and helping others to have an easier time getting ADR's.
In this case, I think having a cc hold with a 72 hour policy would not help solve the double booking problem but would instead punish those who have a legit reason to cancel. If this policy were to be put in place, what would keep the "double bookers" from still making 2 or 3 ressies and canceling them 72 hours before? They would still be keeping others from getting the ADR's until 72 hours before. It might keep some from double booking but I still think a lot of ppl would do it knowing they can still cancel 3 days before.
I think a better solution would be something to keep ppl from ever double booking in the first place. If the dining CM's would ask each person trying to double book to cancel one of them at the time of the call it would help some.
I know some ppl book using different names and phone numbers. Why can't they do it like the hotel ressies? Ask for the name of each member of the dining party so they can make sure none of those names have another ressie for that day and time? They could also require that the main person on the ressie be present for the meal (just like the hotel) so ppl couldn't book under the name of another person who isn't going. I know that would take more time on the phone but it might be worth it. Most familes are probably going to be making the ADR's for the same people so they would only need to ask once unless a party planned to split up for certain meals. In that case they would still have the names and would just need to ask which ones for which meal. For those who split up they could just put one ressie under the name of one of the ppl attending that meal and the other under the name of someone attending that one. I'm sure there is a way to have the computer system check the names for other bookings. This would be very easy with an online booking because we could each enter all of the names ourselves and the computer could check for other bookings and prevent anyone from entering the name of someone with another ADR for that day and time.
I'm sure there are many reasons why this idea wouldn't work and I am fully expecting to hear them but right now this is the best plan that I can think of to prevent double bookings without punishing those of us who might have to cancel at the last minute for other reasons. I'm sure there are other things that might work as well but I doubt Disney will do any of them as long as they are not losing any money.