The website MarketingCharts.com offers some interesting charts as well as explanations that tell how people make use of social networking sites. Check out Younger See More Soc Net Benefit. Just a few paragraphs down on the same page is a section that describes the social networking habits of middle age and seniors — Older Soc Net Dramatically Rises.
Take a look, also, at some of the charts that depict all sorts of World Wide Web user statistics. Links to a few interesting charts are below.