Overall, the market share of U.S. visits to the social networking custom category decreased by 1% in May compared to April, and has decreased 6% year-over-year.
Among the top 10 social networking Web sites, Facebook ranked second by the market share of U.S. visits with 16.24%, followed by MyYearbook, which received 1.40%.
According to Hitwise, MyYearbook experienced the largest gain in market share in May among the top-five-visited websites, increasing 384% compared to May 2007.
Facebook and BlackPlanet followed, increasing 42% and 9%, respectively.
--Gavin O'Malley