On Sept. 5, 2006, Mark Zuckerberg changed the way that Facebook worked, and in the process he inspired a revolt.Zuckerberg, a doe-eyed 24-year-old C.E.O., founded Facebook in his dorm room at Harvard two years earlier, and the site quickly amassed nine million users. By 2006, students were posting heaps of personal details onto their Facebook pages, including lists of their favorite TV shows, whether they were dating (and whom), what music they had in rotation and the various ad hoc “groups” they had joined (like “Sex and the City” Lovers). All day long, they’d post “status” notes explaining their moods — “hating Monday,” “skipping class b/c i’m hung over.” After each party, they’d stagger home to the dorm and upload pictures of the soused revelry, and spend the morning after commenting on how wasted everybody looked. Facebook became the de facto public commons — the way students found out what everyone around them was like and what he or she was doing.But Zuckerberg knew Facebook had one major problem: It required a lot of active surfing on the part of its users. Sure, every day your Facebook friends would update their profiles with some new tidbits; it might even be something particularly juicy, like changing their relationship status to “single” when they got dumped. But unless you visited each friend’s page every day, it might be days or weeks before you noticed the news, or you might miss it entirely. Browsing Facebook was like constantly poking your head into someone’s room to see how she was doing. It took work and forethought. In a sense, this gave Facebook an inherent, built-in level of privacy, simply because if you had 200 friends on the site — a fairly typical number — there weren’t enough hours in the day to keep tabs on every friend all the time.”It was very primitive,” Zuckerberg told me when I asked him about it last month. And so he decided to modernize. He developed something he called News Feed, a built-in service that would actively broadcast changes in a user’s page to every one of his or her friends. Students would no longer need to spend their time zipping around to examine each friend’s page, checking to see if there was any new information. Instead, they would just log into Facebook, and News Feed would appear: a single page that — like a social gazette from the 18th century — delivered a long list of up-to-the-minute gossip about their friends, around the clock, all in one place. “A stream of everything that’s going on in their lives,” as Zuckerberg put it.