Earlier quoted context omitted.
In a similar vein, a good friend of mine (+ all his family, about 10 in all) was kicked out of an AirBnB at the last minute because it had been double-booked on Booking.com at a higher price, and had just been rented via that site. I've come across a few such stories.
A family member of mine had something similar happen when using booking.com. She showed up at the hotel and they had sold her booked room to someone else. It was late and a bit of a nightmare to find another place to stay. Overbooking airplanes means someone might be stuck sitting in the terminal for hours. Overbooking.com means someone might be made to drive around late at night, tired, with nowhere to sleep.
Another example is Marriot will commonly let the local management control inventory. They commonly use the cheapest room to book to max capacity and upgrade people until they are fully booked. It almost never makes sense to book a more expensive room unless you are booking within 30 days.