I won't touch AirB&B. I joined the Porto facebook group as I was moving to Portugal. I left because they were all people who bought property in Porto and are now renting them out at skyhigh prices.

Due to my peculiar circumstances, I have lived on three continents during the past 7 years (America, twice in Europe, and once in Africa). All of them have had enromous rental increases and the locals are priced out of the market.