One of the reasons that airlines, restaurants, etc overbook so much is do to the fact that traveler's make double and triple bookings and they know it. I'm sorry, but I disagree with double bookings - it's what makes reservations so difficult to obtain.

On good rates for car rentals in the USA, I'm a member of Hertz Gold - anyone can join it. Hertz gives their Gold customers automatic discounts, upgrades, etc. Plus, they have your car parked up close and they even have all the paper work completed in advance and waiting in your car - no lines. Many times, Hertz has dropped me off next to my car and the personnel there have the car already running and the AC turned on. All extras from Hertz at a discount price - Avis and others offer this too. Bill Sutherland