Last Thursday afternoon before the most hyped class at Stanford University was about to start, instructor B.J. Fogg and his four teaching assistants attempted to solve this engineering problem. How do you cram 100 students into a classroom that only seats 56? Arrange chairs at long tables near the fire exits.

The students, though, didn't seem to care if they had to sit on the floor to take the most popular computer science course this fall quarter: how to create engaging applications for Facebook.

Shelling out steep tuition fees to take a class on the social network of the moment may seem like a good payoff in the long-term, but few developers have yet to turn significant profits from writing Facebook applications. More than 5,000 applications have been created since Facebook announced in May that third-party developers could build on its platform, and only four boast more than 1 million users.

Fogg, who has a background in Web development and experimental psychology, polled his students on why Facebook is the most important social network. "Facebook is the most convenient and respectable way to feel connected to friends, get updated on existing friends, find new people, build relationships and express identities," he says. "For me, the interesting part of the class is to do research with a bunch of experts."