Apparently three-quarters of Economists don't understand the concept of "Opportunity Cost". They only think they do.
This is scary, if not entirely unexpected.
It would be interesting to perform a similar experiment on IT professionals. Take the enterprise space. There are some key concepts you have to understand in this arena if you are to avoid being dangerous.
These are concepts that transcend fads or products. They include a fundamental understanding of transactions, two-phase commit, messaging, object-oriented programming, security, project-management principles and business context (and more).
There are moves afoot to improve the professionalism of the IT trade. They are, at present, experience based. Perhaps there should be some testing of core knowledge too.