Margin goes both ways. So with $1 billion reserves they can shortsell $100 billion worth of stock. To get that much they counterfeit the stock. They can run up the pumps fast as well. The regulatory question and legislative question is do we want to trust these hedge funds to have that much leverage when their reckless risky bets could crash the whole economy accidently or on purpose? It is almost like turning over the Strategic Missile Command to a bunch of coked up hedge fund managers them at live an above the law Jeffery Epstein lifestyle with a lot of political connections and influence over government though lavish donations. Citadel paid Janet Yellen $700 k over the last two years for several speaking engagements (lavish dinner parties for the Uber Wealthy)
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