Earlier quoted context omitted.
And most landlords and cities prohibit AirBnB-style rentals, but that has never stopped AirBnB.
Are you sure about that? You seem to missing any sort of a source.
There are no particular bylaws governing subletting in tenancy agreements, but almost all landlords forbid it. Mine does. Yours probably does, too. AirBnB has not, and will never do any due diligence in verifying that a renter's tenancy agreement permits short-term subletting - they prefer remaining ignorant of whether or not their units are legal.
[1] http://www.nolo.com/legal-encyclopedia/overview-airbnb-law-s...