Black Swans!
By Adam Rifkin
Billion dollar startups go by many names, such as black swans and dragons and unicorns.
Sam Altman observes that no one knows which seed companies will become black swans.
Tod Francis agrees. It's impossible to predict which companies will be swans later.
WSJ Unicorns page: http://graphics.wsj.com/billion-dollar-club/
Fortune Unicorns page: http://fortune.com/unicorns/