Originally Posted by tr3k

Just had to use it. Booked a ticket with an airline which is known for having no 24 hour grace period (and very poor cancelation handling). Expedia gave me almost 3 days (booked saturday, can cancel until monday night). Canceled in a bit over 24 hours - and see the reverse charge preauthorization on the card immediately. Usually with "24 hour" cancelation charge doesn't even hit my card.