Usually when you book a place to stay on Airbnb, there’s a certain courtship period between the renter and the rentee — a back and forth about how to pick up the keys, some questions to make sure you’re not handing your apartment over to an orgy organizer or serial killer. But sometimes you just need a place to stay, and fast. To serve those spontaneous customers, Airbnb is adding instant booking in some cities. [More]