I think short-term rental rules really need to be determined on a community by community basis. In some places (like beach towns, or ski resorts) it might be ok to have 50% (just pulling that number out of nowhere) houses be short-term rentals. In NYC or San Francisco it might make more sense to limit short-term rentals more (a certain number of nights per unit per year), the policing of such a policy though, oi!