Yes, I’ve heard of it, and as a landlord myself, I’d be very angry if I rented to you only to have you turn around and rent it out to a bunch of random strangers, especially without my knowledge.
1. I rented to You. I did my due diligence and ran background checks on you before I decided to allow you to live on my property.
2. In condos, in our area, Air BnBs are illegal per condo bylaws because there’s no way of knowing who you’re letting into the condo building.
3. The rental contract specifies exactly who will be living in the unit. If you put your name down and turn it into an AirBnB, you are in breach of contract and I will evict/sue you, whatever is more appropriate.
However, if you were upfront about your intentions, and you aren’t breaking any laws, then sure...go for it. I think I read an article about someone in SF who did it with four rental units.