The Dunning-Kruger Effect, named for psychologists David Dunning and Justin Kruger, is all about the most vicious problem of ignorance: if people don't know much about something, they also don't realize how little they know. They tend to overestimate their skill in that area. Worst of all, they don't know which "experts" to believe on the topic, so they're easily led astray by those who are smarter and want to manipulate them for profit or power.
This has depressing consequences for democracy. Topics that are rather technical — macroeconomics or global warming or health care policy or old age pension systems — require study and thought to understand. The average voter who hasn't looked into them in detail is likely to be snookered. Society suffers.
And this form of blindness to one's own blindness is an old story. Wikipedia offers quotes from Charles Darwin ("Ignorance more frequently begets confidence than does knowledge") and Bertrand Russell ("One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision"). And William Butler Yeats said it even better in his poem "The Second Coming":
|The blood-dimmed tide is loosed, and everywhere|
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.