For something to be a logical extension, it has to derive from the other. That would mean that the community of Portland would need to benefit from AirBnB rentals as well as the renter and rentee, which seems difficult to prove given the recorded effect of AirBnB in other areas.

The same with Uber - for the "sharing economy" to be a logical extension of communitarianism, the greater population of Portland needs to derive some utility from people providing and using Uber service.

I'm a huge skeptic of Uber's explotative labor practices and general shadiness, and I think "sharing economy" is doublespeak marketing BS. But credit where credit is due, the greater population of Portland might well realize some material benefits from Uber, via reduced drunk driving (or reduced drunk ironic fixed-gear cycling, as the case may be).

It's not a logical extension because most of these "sharing economy" companies are a) subverting the rules and sovereignty of the communities in which they operate, b) introducing parasitic drag in the deployment of capital in those places, and c) creating a disconnect between local owners and local consumers--in effect, you do business with Uber, not Francine the cabby.

Orthogonal to all that, of course, is the generally scummy practice of reducing these folks to serfdom.