The good news for Facebook is that some two-thirds of online American adults are Facebook users, making Facebook still the dominant social media site in the U.S. And social media use generally continues to grow: 69% of online adults report using at least one social medium (which translates to half of the entire adult population of the U.S.); 92% of social media users maintain a Facebook profile; and people are using social media more frequently than before - 41% indicate accessing social media sites several times a day.
When asked about the value of Facebook in their lives, more users reported Facebook becoming less valuable and important in the last year (28%) than thought Facebook had become more valuable and important (12%). In addition, more reported their use decreased over the last year (34%) than indicated that they had increased their Facebook use (13%). The bad news for Facebook is that the declining use is highest among the key demographics advertisers want to reach. In the key 18-29 age bracket, 42% of users reported decreasing their time on Facebook in the last year; among those 30-49, 34% reported using Facebook less.
It would seem that Facebook has been morphing from the hip, cool, must-have app for the younger generation, to a useful tool for keeping contact with friends and family as people move and disperse. As for the younger generations, other research results suggest they're not abandoning social media; rather, they're shifting their focus to other social media sites - Twitter in particular.
Source - Coming and Going on Facebook, Report from Pew Internet & American Life Project