Hotels and boarding houses do make an imposition on their surrounding communities. Having taxes and zoning requirements on them to compensate for that is reasonable, and most of AirBNB's "edge" comes from violating those laws.
Noise pollution and additional crime experienced by neighbors from the short-term guests staying at Airbnb locations would qualify as an externality. Higher occupancy in Airbnb locations stresses capacity in pools, parking, gyms and other amenities of the neighborhood or complex is also an externality.
