Airbnb, the San Francisco-based bed and breakfast startup, has successfully helped to win an appeal for one of its users whose landlord was fined $2,400 for renting out his apartment for three nights. The East Village tenant, Nigel Warren, fought the ruling with his landlord, Abe Carrey, and Airbnb, with the primary argument being that renting a room does not violate the law, as long as a resident under the lease is present during the guest’s stay.