You should really watch this talk by Ben Horowitz [1]. The takeaway here is that they look to explore "good ideas that look like bad ideas," and he goes on to talk about Air BnB and some other companies.

I bet this is one of those types of investments -- it is actually a good idea but looks like a bad idea right now (by conventional wisdom).

[1] - http://a16z.com/2014/11/12/how-can-large-companies-innovate/