Hedge fund manager Bill Ackman just disclosed a position in Uber. Bill Ackman is one of the most closely followed investment personalities on Wall Street. As CEO of hedge fund Pershing Square Capital Management, Ackman has been at the center of some creatively structured investments in recent history.

Maybe Bill Ackman has. He said he has been "a long-term customer and admirer of Uber beginning when Edward Norton showed me the app in its early days," "I was also fortunate to be a day-one investor in the company through a small investment in a venture fund,

Last week, the stock of Uber Technologies went on a wild ride, falling hard after Uber reported earnings on Feb. 5, only to rocket higher toward the end of the week. On earnings, while revenue and earnings per share actually beat expectations,

Go big or go home. Billionaire investor Bill Ackman of Pershing Square Capital Management takes that sentiment to heart. His hedge fund has some $13 billion in assets under management, but he owns just 10 stocks (track his portfolio here),