Some of the most famous companies of the 21st century, such as Uber and Airbnb, seem to be built upon the destruction of fences. Uber obsoleted taxi licenses and Airbnb the lengthy process of befriending the owner of a house where you’d like to live for a week. However, Uber and Airbnb didn’t merely destroy the fence. They acknowledged its use and built a surrogate. Uber gave drivers something else to lose: a 5-stars rating. Similarly, Airbnb introduced a two-way rating system and provided (limited) insurance to both home-owners and visitors. In fact, in a previous essay, I argued that Uber and Airbnb are Trust-As-A-Service businesses: for a fee, customers can buy trust in transactions with strangers. Chesterton's Fence