Every time I hear about airbnb though, I wonder - don't you need a permit to offer paid accommodation? For example in my part of the U.S. you need a "special use" permit to run a B&B. How is advertising your spare room on airbnb different?
I looked in their FAQ but couldn't find an answer.
I don't think the collusion is necessarily overt, but most businesses welcome this kind of barrier to entry.
Granted there are also financial interests at stake, for example the state collecting a hefty room tax when people end up in hotels. But then that money goes to infrastructure among other things, so there is some method in the madness.
The entrenched businesses don't want any competition from this here new-fangled internets.