Airbnb might inadvertently fix you up in a unit that's owned or rented by a violent person with a key to the place. Horror stories are starting to appear. Last spring, one hapless New Yorker rented out his place and was evicted immediately when the landlord found out what he'd done. Another woman rented out her place and returned to find condoms and diaper wipes; her "guest" was a prostitute. Still another came back to a trashed apartment where an orgy had been staged.