According to Citi, Facebook now accounts for a whopping 16% of time spent online by U.S....

|By:, SA News Editor
According to Citi, Facebook now accounts for a whopping 16% of time spent online by U.S. Internet users, compared with 11% for GOOG's sites, 9% for YHOO's, and 6% for MSFT's. Analyst Mark Mahaney expects this growing share of web usage to continue fueling Facebook's massive ad revenue growth. (previously)