I think hotels have cut back drastically on this, now that most reservations are guaranteed with a credit card. At some magic hour, say 5PM, they charge everyone's credit card for the night whether they checked in or not. For most of the reservations I've made in the past year, the cancellation period is actually one day prior to arrival.

In years of business travel, where I frequently arrive at the hotel at midnight, I've only been walked three times. Once at a trade show, where the hotel was renovating and didn't get the rooms done on schedule. Second, where a guest got ill and was unable to depart on schedule. Third, on a trip to New York, where they walked me to a sister property located literally across the street (I got the feeling that these two hotels frequently traded guests).