Facebook continues to lead all social sites in ad revenue, reaching an estimated $3.8 billion in 2011, double the $1.9 billion in ad sales the year before. Facebook also has widened its lead in the display-ad market, with 27.9% of monies spent in the U.S. last year, ahead of Yahoo with 11%.
LinkedIn ad revenue hit $154.6 million last year, up 95% from the $79.3 million the year before. EMarketer estimates that LinkedIn's ad sales will cool somewhat this year, growing 46% to $226 million. Twitter ad sales grew 233% to $139.5 million, up from $59.9 million in 2010. The report estimates that Twitter's international growth will push ad sales to $259.9 million this year, a year-over-year rise of 83%.