I still feel like there are going to be some major regulatory changes that will eventually hit these types of businesses. What we've generally seen is cities say no, then realize how much value there is but not know what to do about it, then say yes. What we haven't seen as much is the post-yes interaction, where additional taxes and regulations get established. Should be interesting.
AirBnB provides little to no value to most cities. Cities lose out on all of the taxes and revenue when someone uses AirBnB instead of a hotel. The types of people who use AirBnB are heavily price sensitive, so the lost tax revenue isn't made up by increased spending elsewhere, i.e., on goods, dining, or tourist attractions.
Also, there's no need for "post-yes" for AirBnB. They already have hotel taxes and regulations (which cover everything from major chain hotels to tiny bread-and-breakfasts).