At the beginning, Sebastian Thrun structured his web lectures as he did over, during two decades, at Carnegie Mellon and Stanford. He recognized himself as a tough teacher: "I always gave students really hard questions, I always let them fail and I would come to the rescue. [It] made myself really smart", he said.
The strategy to give students hard material it is called "sink or swim". In the middle of his epiphany moment, Thrun said: "We really empower the professor to make him look smart and we don't help the students to become smart".