Wish to point out if a hotel is still overbooked at the "deadline" (was 6pm DOA up until recently), it should know that it has a problem and should act proactively as they are financially compensated/protected with cancellation fees.

If giving away a room to a walkup with open reservations for the night then they are trying to collect double for the same room! And should suffer severe penalties although again the the financial implications are not as great if getting paid twice for the same room.