Whats the demographic sweet spot for users of social networks? Not what you think. According to a study released by Pingdom, a web monitoring provider, 25% of users of social networking sites are between 35 and 44, and 57% of the users are older than 35.

This is a mainstream media audience with significant purchasing power and an investment in social tools.A breakdown of age distribution by leading social network sites is even more instructive. Bebo and MySpace are the youngest sites, each with more than 40% of their users under 24. Facebook is one of the most balanced sites in terms of age distribution. Twitter, Delicious, LinkedIn and Classmates.com skew the oldest.The older-skewing sites, interestingly, are focused largely on content-sharing or connecting. The design of LinkedIn, for instance, is highly focused on organizing your professional information, but doesnt give a full-spectrum of communications tools.

The second chart is a little misleading, in that is doesnt reflect the dominance of Facebook in terms of members and audience.

The data was aggregated using Google Ad Planner.