Venture capitalist Bill Gurley is more worried about Elon Musk being 'too risky' than he is about Mark Zuckerberg. : Facebook stock was a controversial subject at the annual Sohn Investment Conference in New York Monday, where hedge fund managers and top investors take the stage to present their best investment ideas. Jeff Gundlach, the renowned bond investor and CEO of DoubleLine Capital, announced early on that he was shorting, or betting against, Facebook stock, in light of the social media company’s recent data leak woes.