Sadly, we're at the stage of this "crisis" where parody is the only appropriate response.
Does someone who rents two houses count as "investment properties"? How about someone who owns a complex with 50 units? How about a corporation that owns a complex with 500 units?
1) Occupied at least a certain portion (let's say 10%) of the year
2) Occupied by the owner at least twice as often as occupied by non-owners
Can be considered a personal residence in my book. Anything not meeting this is an investment property.
What I mean, is that laws are useless if there is no means to for them to be seriously enforced, which is the case where I live.
On the other hand, if I were to create my own Airbnb website in that same country, I'd be shut down by the end of the week and put in jail facilitating illegal renting listings, while Airbnb executives risk absolutely nothing since they live in USA.