The counterargument lies in the very text you wrote. It was a very loosely-regulated group of supposedly self-interested investors, bond traders, and banks that killed any idea that unregulated capitalism can somehow govern itself (not unlike BP's boneheaded disaster in the Gulf). The internal structure of the banks and corporations have been proven to be just as incompetent as the worst governments. They created the very weapons of their own destruction.
The result of too-big-to-fail banks and insurance companies suffering the "natural result of their actions" would have been a nuclear-war-equivalent destruction of capital that they knew would never be allowed to happen. The only way to prevent it would have been aggressive anti-trust action to break the banks into small-enough-to-fail pieces.
The irony of your last statement is that continuing to allow corporate power to be concentrated into fewer hands ultimately leads to the "perpetual serfdom to the landed classes" you seek to avoid. At least we can occasionally vote incompetent politicians out of office.