Conforming to group consensus at the expense of critical thinking. Everyone agreeing doesn't mean anyone is right.
Leads to poor organizational decisions, suppresses innovation, and explains why diverse teams often outperform homogeneous expert teams.
Groupthink contributed to major disasters like the Challenger explosion and Bay of Pigs invasion - smart people making terrible collective decisions.
"Statistically speaking, you're probably wrong about statistics. And about speaking, for that matter."