My favorite example of this was the attempt, by the Hunt Brothers, to "corner" the silver market in 1979/1980: "But on January 7, 1980, in response to the Hunt

My favorite example of this was the attempt, by the Hunt Brothers, to "corner" the silver market in 1979/1980: "But on January 7, 1980, in response to the Hunts' accumulation, the exchange rules regarding leverage were changed, when COMEX adopted "Silver Rule 7" placing heavy restrictions on the purchase of commodities on margin. The Hunt brothers had borrowed heavily to finance their purchases, and, as the price began to fall again, dropping over 50% in just four days, they were unable to meet their obligations, causing panic in the markets." https://en.wikipedia.org/wiki/Silver_Thursday https://en.wikipedia.org/wiki/Silver_Thursday