According to research by comScore MediaMatrix, social networking sites are no longer dominated by teenagers. Older demographics are starting to become the majority in many social networks, owing to the aging of the population and other factors that drive the not-so-young set into connecting with peers and contacts online.

… 68 percent of the 55 million MySpace users are 25 and older, while 71 percent of the 1 million users on the declining Friendster fall within the same demographic. Even Facebook, which up until recently was limited to college and high school students, boasts of a growing audience 15 million users - 50 percent of whom are 25-plus. Contrasty, the smaller and less popular Xanga.com is considerably younger, as 20 percent of its 8.1 million user base falls within the 12-17 demographic.

The relative aging of the giant social networks indicates that their recent exponential growth has been driven by new and older Web users discovering the phenomenon. For example, back in August of 2005, teens made up a quarter of the MySpace audience. Now that group represents just 12 percent of users. During the same period, the middle-aged crowd has been gravitating to the site in droves: adults 35-54 now make up more than 40 percent of the site, up 8 percentage points in the last year.

There was a time when social networking sites were just for that–social networking. Nowadays, however, sites have been developed for more than friend-adding, photo-sharing and testimonial-giving. Professional networking sites have started to become popular, particularly among online/connected professionals and businesspeople who get leads for business deals and jobs through these sites. Social networking sites are great for developing business relationships, especially these days, when transactions can span continents. I, for one, have had experience with organizations hiring not via the traditional channels (job ads, resume gathering, interviews), but from contacts on professional networking sites. Indeed, it’s not what you know, but who you know.