Whats really missing from this article, and is alluded to quite frequently, is couchsurfing.com
I skimmed the article, seems like a great pitch, but I didn't get why I would want to use airbnb.com over couchsurfing.
couchsurfing.com is pretty mature though not w2.0. It's got the verification system so you can have some peace of mind, and its free.