1. Facebook
It was 2004 when Mark Zuckerberg started asking his fellow Harvard University students to try out his new idea known as "the facebook." The online community allowed his peers to create personal profiles, search for friends’ profiles and invite others from the university to join. It was a smashing success almost immediately.
Half of the Harvard undergraduate student body had Facebook profiles within a month of the site's launch. After being limited to academic institutions for two years, Facebook opened to the general population in fall 2006, and just three years after its launch, the site had 30 million users. Zuckerberg soon extended the site to allow students from universities in the Boston area to join. Before long, he opened the site up to students from any university in the United States. The site continued to grow. In 2006, Facebook opened its virtual doors to anyone with a registered e-mail address.
Since then, the site's popularity has exploded. Not content to rest upon his accomplishments, Zuckerberg continued to push for new features. One of the most revolutionary was creating an application programming interface (API) for third-party developers. Suddenly, programmers could design applications that could tap into Facebook's massive population. Applications range from simple games and diversions such as Lexulous to clever marketing campaigns like Burger King's short-lived Whopper Sacrifice application which asked you to delete 10 friends to earn a free Whopper sandwich.
Want to get silly with friends by sending them a virtual beer or flower? Go ahead. Want to dabble in clever marketing campaigns from soft drink companies? You can do that, too. You can also participate in some of the hugely popular apps such as iLike for music, Places I've Been for the wanderlust or Flixter for movie fans.
In short: Facebook has become the most visited social networking site in the world, receiving more than 10 million unique visitors than MySpace in January 2009, making it the No. 1 social networking site on our list.
