In a monthly view of U.S. Internet activity for top parent companies and web brands, The Nielsen Company found that the average time users spend using Facebook per month grew nearly 10%, topping seven hours during the month of January.

Also noteworthy, the number of those actively using the web grew 3.8%, to slightly more than 203 million users, according to the report.

Source: Nielsen Company
http://blog.nielsen.com/nielsenwire/online_mobile/facebook-users-average-7-hrs-a-month-in-january-as-digital-universe-expands/