If the problem of small change led economists to understand how to run a system of token money, did some of the greatest economists of the early 20th century learn the wrong lesson from the system's success?

ECONOMIST: The lessons of sound money from 1,000 years' experience

This is teaching my immune system a lesson now.

WSJ: This Is One That's for the Spartans

That was the lesson of the European Monetary System debacle of 1992-93 (and, arguably, of the downfall of the pegged-but-adjustable regimes used in Asia until last year).

ECONOMIST: One world, one money

In the pre-K class Karen Simak, a 44-year veteran of the Chicago school system, is focusing her efforts on a broader life lesson--planning ahead.

FORBES: Kindergarten Lawyers

But Exxon Mobil is learning a different lesson: Don't get sued in Alabama--its legal system is annoying.

FORBES: Disaster Of The Day: Alabama's Natural Gas

Kentucky legislators learned their lesson and eventually repealed several of those laws, and the health insurance system revived.

FORBES: Don't Fight Crime with More Health Care Mandates

California is only one of many states not to have learnt the lesson from Florida: 25 other states still use the old punch-card system.

ECONOMIST: Californian politics

And I learned an important early lesson of the coming digital age: once your data exists, it is in the system, and the people who control the system can see it.

FORBES: Bloomberg Isn't The Only Company Able To Spy On Users

And we assumed that banks had learned their lesson from the 2008 financial crisis and were taking steps to prevent employees from trying to work the system.

FORBES: How Did Carnival, Boeing, Barclays, and Tesco Squander Our Trust? How Do They Win It Back?