Too Long; Didn't Read
Google, Facebook, Youtube, Amazon, Uber and a phone book have in common: they are indexes — searchable lists of stuff. Most online unicorns are essentially just indexes with a nice user interface and customer support. The downside is that these companies become central points of tremendous power — in other words, single points of failure. They are private companies that can quite freely favor or discriminate against whomever they like. There have been calls to regulate online platforms as public utilities akin to banks or electricity companies.