Why did a minor math error that would occur only once every 27,000 years so enrage customers that it briefly threatened to derail Intel’s Pentium chip? And how could a feature as trivial as an inexpensive cup holder swing millions of customers to purchase a $17,000 automobile—particularly when only three years later, the same cup holder had become almost invisible to buyers? Is it possible to develop rational product strategies in the face of apparently irrational customer behavior?