Uber's first-ever employee Ryan Graves, a billionaire due to his equity in the company, was hired through a tweet. In 2010, Uber Co-founder Travis Kalanick had tweeted, "Looking 4 entrepreneurial product mgr/biz-dev", to which Graves replied, "email me", and became Uber's first employee on March 1 that year. Uber made its IPO at the New York Stock Exchange on Friday.