AirBnB at this stage (Apply HN is prototype-stage) would have fallen into Network Effect and Lifestyle Business (the size of market for sharing airbeds at conferences is small), and not into Unicorn Embryo.
I would not put the original AirBnB into the lifestyle business category, but the non-profit category. If you look at how many people use AirBnB to share an air mattress in their living room to strangers it was an idea that would never have made money. It was only when they pivoted to their current approach that they became a huge success.
Actually AirBnB is a good example of how you can solve the chicken and the egg problem with networks. Because real estate rentals are local, it is possible to bootstrap a strong network in a geographically small location and then scale out. All the successful network businesses out there have used a similar approach (Uber, Facebook, etc).
I don't see how AirBnB would ever be classified as Lifestyle Business. The intent was never to make a small amount of money at a fixed scale. It was always about huge scale, which is almost always at odds with a Lifestyle Business.
Network Effect yes, Lifestyle Business no.
Further, any given investor would be wise to look at businesses like AirBnB with skepticism from a "can they actually achieve critical mass of users" point of view. Effectively 0% of these types of businesses are unicorns. Unless you personally have special knowledge or are willing to take an extreme risk, it's foolish to invest in these ideas and it amounts to literally buying a lottery ticket.
