After reading some more, I think I have a more detailed look as to how he blew up.
Oddly, it was actually very safe bets he was making! But it is how you go about it...
So it looks like he was selling options such that you would expect to 'win' 99 times out of 100. But of course, the 'pay off' for that kind of bet is very small (< 1%). So he tried to make 'big money' by leveraging this bet with borrowed money.
So you make 1% four times a year (options 3 months out) is 4%, but you use a 10x leverage for 40% a year. It works until it doesn't.
He apparently wasn't even diversified, and had so much in Natural Gas options, that the move in NG wiped him out and more.
The 4th post down on page 2 by srinir gives some examples.
https://www.elitetrader.com/et/thre...to-blow-up-his-fund-and-clients.327102/page-2
A $4 call sold for 1.5 cents when NG was ~ $3. If the call expires and NG is less than $4, he gets to keep his 1.5 cents. But NG went up to ~ $5, so the call that he SOLD is now worth ~ $1 ($5-the $4 call strike) - he would need to cover/buy it back at ~ 66x what he sold it for! Double-plus-OUCH!!!
The financial firm behind those options isn't going to let that go on any longer, so they liquidate him to cover as much as they can. It apparently rose too fast to catch it all, so he went negative.
What he needed was an offsetting position that would limit the maximum loss he could have. It's been a while since I studies options, but I think what he would need to do is BUY a CALL at a strike price little above the $4 strike he sold, say $4.10. Then the max loss would be 10 cents on the 1.5 cents he sold for. But of course, the $4.10 strike call will cost him only a little less than what he sold the $4 call for, so there is little profit to be made. So he went 'naked' to maximize profits. And he got hit, big time. Not only the 66x, but if he was on 10% margin, that's like 660x against you!
I'm sure those details are wrong, but it explains the concept, I think. A classic Taleb "Black Swan" story, though this Black Swan should have been expected - it just would not be that uncommon. In fact, I think Taleb does something like the opposite of this - his data says the bets that only pay off occasionally are often mis-priced, and if you make enough of them you come out head?
-ERD50