Consider Stanford’s experience: Last fall, 160,000 students in 190 countries enrolled in an Artificial Intelligence course taught by Mr. Thrun and Peter Norvig, a Google colleague. An additional 200 registered for the course on campus, but a few weeks into the semester, attendance at Stanford dwindled to about 30, as those who had the option of seeing their professors in person decided they preferred the online videos, with their simple views of a hand holding a pen, working through the problems.