Free markets are like pretty much any element north of Plutonium - the half life is extremely short and if they are forced to exist in nature they'll quickly decay to a more stable state... often violently and sometimes with a loud bang.
Got a case history?
> it's generally under appreciated just how unstable free-markets are.
Freedom does require eternal vigilance, that's for sure.
> the half life is extremely short
The US has had one for what, 240 years now?
I guess if you want to call that entire 240 years "capitalism" and use that as evidence that it's, ah, more sustainable than other strategies, well that's fine, but that means free market capitalism has no mechanism preventing things like slavery or company towns. In fact it seems it continually fails to provide for anyone other than capital holders until another philosophy enters the picture, such as government regulation or worker's unions.
You say freedom requires vigilance, what's that mean? When the only way to eat was to work in a company town and scrape together barely the means to a living, everyone is vigilantly aware of how shitty the situation is, so then what? History teaches us the "and then what" is strike followed by reactionary state violence followed by bloody revolution, so there's your case history of devolution to violence.