While cathartic, I'm not sure how much benefit complaining about double booking does. Doing so ignores the benefits that the Disney dining system derives. For your consideration:
1) The dinner in Germany and dessert in France crowd. By making close double bookings, people can enjoy the signature fare from the many different restaurants throughout the parks. Perhaps they want to try the OGTC at LTT, but they aren't interested in the meal. So, they go to Tony's for lunch at noon and LTT at 1. A double booking, yes, but neither "meal" will be as long as it could have been. Someone demanding that individuals not do this so that they can have an ADR at LTT bespeaks the demanders selfishness. Indeed, the short meal may even lead to an opening for someone to obtain a walkup slot.
2) If Disney offered a 24 hour courtesy overlap, you might find fewer DBs as people would have the opportunity to discuss plans with spouses. There are a lot of folks here who have spouses that are happy with whatever the planner decides, but there are plenty of folks where both partners take an interest in activities, but can't be together all day, every day. Instead, the system is designed such that there is no reason not to double, triple, quadruple, quintuple book if you are not sure what the two of you will agree on. Since the ADR doesn't expire, the incentive to bring the matter to immediate attention does not exist. Coupled with spotty menu coverage for the non a la carte restaurants, the decision can take even longer.
3) By opening the ADR period before the free package cancellation period ends, individuals are placed in a situation where the prudent course of action is to make ADRs before finalizing the itinerary. Since some ADRs are more difficult to obtain than others, the prudent decision it to make unnecessary reservation in case your dates will overlap. Of course, by reducing the timetable, holder of ticket only options or local residents who frequent resort locations are unnecessarily affected.
4) Double Booking actually alleviates pressure on the Disney dining system. By having missed reservations, gaps are created throughout the dining day that allow the restaurant to catch up to attendee reservations. The, "we're currently running about one hour behind," would be higher if all ADRs were made and filled.
5) Split parties. If Disney had a better reservation management system, perhaps there would be less need to do this, but the only way to potentially bring all ADRs under a single umbrella is to create multibooking situations. The part of 5 adults decides they want to eat at three different places - 2/2/1. Under a DB ban, two of those reservations must be made under another name, and thus not associated with the main group. Without the data, I can't state it as fact, but I would wager that forgotten details is a top five reason for missed reservations. Or is it not fair to others that people wish to split their parties?
6) Why not have a significant precharge to a CC that would be refunded if the reservation is cancelled 24h in advance or if the diner shows up. I would suggest taking the average cost of an entree at the location and charging that per person. Of course, folks on tighter budgets may not be able to afford to make ADRs, but fair is fair - people shouldn't be making reservations they couldn't afford keep. Unfair, you say? Why? If we are going to stop people from making reservations they can't make, why not stop them from making reservations they can't make at the time?
7) Complaining about double booking is akin to complaining about reservations. After all, why should someone be able to book a table 190 days out when I can only book 180 - we are all going to Disney parks, and the resorts are open to everybody. Or why can people make reservations? I'm left with choosing a lesser dining experience because the demands of my position leave me with only 30 days advance warning on when I will have enough time to go to WDW. Tables should be first come first serve for all location all the time. So on and so forth.