I think it is, in the specific case of the generation Facebook initially targeted: college students in 2004. It's enough time for most of them to get their first job or two, and for some large fraction of them to start building a life with different requirements than college life.
Many of them will have gotten married (median age of first marriage in 2007: 27), and some will have had kids. There's a dramatic shift there: most "family" people I know tend to expect more privacy and control over their lives, and be less focused on expanding their social life and sharing details with their friends. But this is anecdotal, I know: I'd love to see a study on how social networking use patterns change during this age shift.
Many of them will have gotten married (median age of first marriage in 2007: 27), and some will have had kids. There's a dramatic shift there: most "family" people I know tend to expect more privacy and control over their lives, and be less focused on expanding their social life and sharing details with their friends. But this is anecdotal, I know: I'd love to see a study on how social networking use patterns change during this age shift.