Taking the whole family on a beach vacation this summer? Want an apartment in the big city for a long weekend? Why, you’ll need to book an Airbnb rental for that, right? Sure, if you want to run the risk of being secretly filmed by your host, as one couple recently discovered was happening to them at a Longboat Key, Fla., rental. Or if you’re OK with the possibility that your host might cancel your booking at the last minute for no reason or because of your race, as occurred in February with a Big Bear, Calif., rental. Or if you don’t mind that the place you’re renting might not have the proper insurance, safety measures or even be legally available for short-term vacation rentals.