Former Zillow-er, Drew Meyers, is a very social person. He's so passionate about bringing people together, that this is his second start-up to that effect. And it's certainly an interesting one.
Airbnb helped (poor) people make money from the place they were renting (usually to help pay their rent). What made/makes Airbnb cool, was the social aspect: your 'host' being a friend in the city and a tour guide.
What Horizon hopes to do is take it one step further: extract the cool from the money making.
It'll be interesting to see what Drew and Co come up with, but I'd like to see what their community of friends do with the new-found ability to 'stay' with each other.
My guess is, you'll get rampant adoption through the hostel-hopping community, with a fringe use for bed-hopping.
See more here: http://www.horizonapp.co/