Hedge fund billionaire David Einhorn's Greenlight Capital recently acquired a stake in Twitter. :
The start of the new year brings fresh optimism to many investors, and David Einhorn may be first among them this year. Einhorn's Greenlight Capital has suffered a string of setbacks in recent years, and the billionaire investment giant is no doubt looking for a way to start off 2018 strong. Einhorn recently revealed to his investors in a quarterly letter that part of his plan to reinvigorate Greenlight Capital entails a new position in Twitter (TWTR), which he believes is undervalued compared to Facebook (FB).