A 20-minute lightning talk presented at IxDA Interaction 11 on Feb 12, 2011. The tried-and-true "Don't Make Me Think" principle doesn't always hold. Discover how carefully placed friction in an interface can actually improve user experience by encouraging people to slow down and think. Complexity itself isn’t bad; the trick is making complexity seem uncomplicated. Explore examples of websites and mobile apps that incorporate friction without frustration, with elegantly simple interfaces that nevertheless deploy complex interactions to involve users, prevent errors, improve data collection, and create more immersive experiences.