[CrazyStat]

The broker calculated the margin requirements based on the assumption that the price could not go negative. So the investors thought they were risking $30 per contract when it was actually a couple orders of magnitude larger than that.

Effectively the broker lied to them about how leveraged they were.

[sokoloff]

Anyone who thought they were risking a max of $30/contract has no absolutely no business trading futures. Most of them are 1000bbl contracts and the disclosure docs that you read before being granted trading enablement are crystal clear. The margin required to be posted is not the limit of what you can lose. (If it was, margin calls would be much less of a thing.)

[CrazyStat]

The margin is a measure of how much you might reasonably expect to lose. IB was clearly miscalculating it.