IIRC, Ballmer at one point went double or nothing, margining his stock to double his position. That explains half of his stake right there. That's when he was

IIRC, Ballmer at one point went double or nothing, margining his stock to double his position. That explains half of his stake right there. That's when he was worth $100 or $200 million, not long after the IPO. Jim Treybig of Tandem Computers did something similar when he lost half his stock in a divorce.