AirBnB might benefit the customer, but can negatively impact others in the area. For example, if someone is renting out an apartment in a secure building, just giving the keys to an arbitrary someone you're decreasing everybody else's security. Similarly for a house, if a house is being regularly rented by different people, it impacts the rest of the neighbourhood.

In my building, renting out with something like AirBnB is against their occupancy agreement. While I don't know everybody in my building, I certainly know everybody on my floor. I used to know everybody in the building, but a number of people have moved out and I haven't learnt all the new people yet. I'd be really pissed if I found out that someone was offering an AirBnB rental right next to me.