(View this timeline as it appeared in the Bulletin)
1978: Computer bulletin boards appear.
1997: SixDegrees.com is born-the first true social networking site (with profile, friends list). It folds in 2000.
2002: Enter Friendster. It will fade in U.S. but remain popular in Asia.
2003: LinkedIn launches, focusing on professional connections. It now claims more than 90 million users.
2003: MySpace enters the picture, attracting indie bands, artists, teenagers, and the urban social crowd. By 2006, it will pass 100 million members, becoming the country's most popular social networking site.
2004: Harvard sophomore Mark Zuckerberg starts Facebook, which quickly colonizes college campuses, welcomes high schoolers in 2005, and opens up to everyone in 2006.
2004: Google launches Orkut, which will become a major social networking site in India and Brazil.
2004: Flickr is created for photo-sharing, and will eventually incorporate social networking.
2005: YouTube enters the scene for video-sharing; it, too, will incorporate social networking.
2004-06: "Passion-centric" sites pop up, connecting strangers based on common interests. On Dogster, you create a "pet page." On MyChurch, Christian churches can post sermon podcasts and collect tithes.
2006: Twitter comes along, with its 140-character "tweets." Who can possibly care? Lots of people: by 2011, Twitter will have an estimated 190 million users.
2008: Facebook overtakes MySpace as the most popular social networking site in the U.S.
2010: Facebook passes 500 million members worldwide.
2011: Tunisian and Egyptian protesters use Facebook and Twitter in organizing revolts that will topple long-standing dictatorships.