Surely an easy way to the bottom of this, given that AirBnB already collects a fee from hosts, is for the city to tax that fee. Unless, of course, they actually care about why hotels are licensed and regulated, in which case, fan hits shit. But as long as they just want money, isn't taxing internet businesses is starting to the norm? California finally passed enforcement on the sales tax for amazon this year.
"Tax" is certainly the big impetus. "Regulate" is the other. Every hotel, motel, bed'n'breakfast and hostel within a city's jurisdiction has to play by the rules; I'm sure they're more than a little miffed that AirBnB allows homeowners to completely skip out on that. Just like Uber is currently facing an existential threat from jurisdictions that established hack licenses for a reason, AirBnB is about to face an existential threat from jurisdictions that regulate overnight hospitality for a reason. In both cases, the companies were founded by people who didn't know the first thing about their future industries but knew that by sprinkling a little webby goodness on it VC funds could be had. The Amazon thing is interesting. It wasn't so much that California decided to start enforcing things, it's that Amazon decided to start paying tax.