Nothing stops Zuck from selling some/all of his shares and buying BRK.A, SPY or treasuries. Sure, if he wants to do it quickly he will need to do it at a discou

Nothing stops Zuck from selling some/all of his shares and buying BRK.A, SPY or treasuries. Sure, if he wants to do it quickly he will need to do it at a discount, but I'm pretty sure it's under 10% if he is willing to spread it over a year or so. You can argue that he is so rich exactly because he didn't diversify. Obligatory Warren Buffett quote: "Keep all your eggs in one basket, but watch that basket closely"