Forrester: Social networking grows up

People in the 35-54 age group are increasingly joiners and creators, while adults over 55 are more likely to be spectators.

However, with so many more adults participating in social networks, it makes sense for companies to create media and advertising campaigns targeted to them in addition to the ones that target younger people, Corcoran wrote.

Only 18 percent of survey respondents don't currently use social networks, compared to 25 percent in 2008 and 44 percent in 2007.