Opera - Facebook is the most-visited social networking site on the mobile web

Unique mobile visitors to Facebook increased 619 percent worldwide in 2009 according to browser developer Opera Software's newest State of the Mobile Web report. Facebook is now the most-visited social networking site on the mobile web, although microblogging service Twitter experienced the biggest year-over-year leap, with unique mobile visitors increasing 2,859 percent in 2009. All major social networking sites enjoyed mobile user growth last year with the exception of Friendster, which slipped 29 percent.

Despite Facebook's continued growth, the site remains the second most-visited mobile website in the U.S., trailing search giant Google. Yahoo, Wikipedia and MySpace round out the top five. Opera page-view growth in the U.S. grew 228.1 percent over December 2008, with unique user growth up 128.5 percent, users now view an average of 276 mobile web pages per month.

For more on Opera's December 2009 State of the Mobile Web report: read this release