I think these technology startups are getting a little carried away with the word "sharing" when labeling themselves as part of the "sharing economy".
To generalize, these companies use technology to apply the traditional brokerage model used in both real estate and public financial markets (minus any licensing and regulation requirements).
Not that these services are bad - many are quite useful - it's just a matter of calling a spade a spade. That, and the sneaking suspicion that these services would not exist, or would not be nearly as successful, if the economy had less of an employment problem...
These services are pretty handy. I've never partaken in any of these things, but I'd love to take advantage of services like Uber & AirBnB. But until I have the funds to justify it, I'll stick to walking & couchsurfing.