I think that while these tactics are grey area for sure (specially in the case of Airbnb), I firmly believe that this would fall in the, for lack of a better word, "hustle" category. I would guess that most of the companies listed here tried multiple tactics, and these are the ones that worked. From my own experience as an entrepreneur, you just have to keep experimenting with various channels until one sticks, without getting too bogged down with the wider implications.
