If this is your first time registering, please check your inbox for more information about the benefits of your Forbes account and what you can do next! Hedge funder Paul Singer has taken in a stake in the social media company—and now wants to replace Jack Dorsey as Twitter CEO and grab four board seats. Dorsey is an unconventional CEO, splitting his time running both $26 billion (market cap) Twitter and $36 billion Square, the digital payments company. This arrangement is part of the reason that Singer’s firm Elliott Management is pushing for change.