Otherwise known as the income that one would have previously obtained by renting a room to a permanent resident. The big difference with Airbnb is that the service is removing potential rooms and roommate situations from the market. I'm not going to say whether Airbnb is a good thing as honestly I'm leaning toward it being a net benefit. But to say it has not made finding a place to live permanently in places like SF and NYC more difficult for 1st time and early in life renters is difficult for me to agree with.

All progress has a price. And often that price is worth the benefit. But let's not pretend there are not people out there that will be worse off in the short term.