Currently in the United States 78 percent of the total population aged 12+ uses social media sites, which corresponds to about 165 million Americans. Facebook is the most visited social media site, accounting for 43 percent of all US visits. The second most popular social media site is the global video-sharing service YouTube with 22 percent of visits. Together YouTube and Facebook dominate two thirds of the American social media traffic. Reddit, Twitter and Instagram are the next most popular with 5.5, 4.9 and 1.7 percent of visits, respectively.

Launched in February 2004 by Mark Zuckerberg, Facebook quickly gained popularity and transformed from a humble university network to what is now a global social media giant with more than 1.6 billion active users. In June 2009, five years after Facebook launched, it replaced MySpace as the most visited social media platform in the United States. Since then, MySpace has continuously lost market share: in March 2010, YouTube moved up to number two; in May 2011, Twitter and Yahoo! Answers surpassed it; and by July 2012 MySpace fell out of the top-10 with only 0.39 percent of visits.

One of the main reasons for MySpace's decline was its aggressive monetization strategy that ran counter to user experience. Heavily advertised site space made it difficult to use, inflexible, and slow while rival Facebook offered users a clean and light site design. Yet, instead of resetting itself to improve its social-networking environment, in-house built MySpace applications and features remained shallow and often buggy unlike Facebook applications created mostly by outside developers. MySpace also stuck to a business model targeted to the music and entertainment audience. These factors contributed to a sharp audience decline and a corresponding outflow of advertisers no longer willing to commit to long-term deals with the site.

While MySpace entered its decline, Facebook rapidly gained market share, increasing from 32 percent of all US visits in June 2009 to 65 percent in September 2011, an all-time high record. Since then the site's market share has gradually declined. Unlike the initial period of the MySpace decine, however, no serious competitors exist yet to displace Facebook. Even Twitter, the closest to Facebook by brand awareness, has lost 0.2 percent of visits since the start of the year giving way to Reddit.