The problem is that's when you arrive to your rented property late on a Friday night with two tired and cranky children, you just want to make the best of a bad situation.
I know AirBnB have an emergency number, but they themselves state on their website that all they will do in a situation like the above is to try and book you in to another AirBnB property or offer you a refund.
I think a lot of AirBnB customers have lower expectations of the service compared to what they would expect when booking into a hotel and AirBnB benefits greatly from this.
After all the AirB part of their name stands for air bed, the whole business was founded on the concept of customers accepting lower standards for a lower price. Now that AirBnB has grown into a quality property rental service it really needs to up it's game in terms of vetting it's hosts and dealing with questionable situations.