Mark Cuban turned down the opportunity to invest in Uber back in 2010, saying he "wouldn't touch a 2mm valuation." Cuban called it his "biggest miss ever" when sharing the email exchange and congratulating Kalanick on Twitter on Friday morning as Uber went public on the New York Stock Exchange. Read Business Insider's homepage for more stories. Back in 2010, long before ride hailing startup Uber became a tech "unicorn" worth billions, founder and former CEO Travis Kalanick offered billionaire investor Mark Cuban the chance to invest. He turned it down.