The share of adult internet users who are involved in social networking online has more than quadrupled in the past four years in the U.S. In 2005, only 8% of adults had a social network profile. As of December 2008, that number was 35%. What motivates those in older generations to go online? Is it the opportunity to professionally network with their colleagues? The answer may surprise you.

More Adults Than Ever

A majority of teens, percentage wise, join social networks, but it's the adults that still make up the bulk of these web sites. That's because adults make up a larger proportion of the U.S. population than teens, reports Pew Internet & American Life Project. So the 65% of online teens actually represents fewer users than the 35% of adults who participate online. Of course, out of that 35%, the adults that tend to join social networks still skews younger: 75% of those 18-24 use these networks, but only 7% of the adults 65+ do.

It's Not About Professional Networking After All

You may think that many adults have joined the online trend mainly to network professionally with others in their field. However, that turns out not to be true. Instead adults, like teens, are there to socialize with their friends and people they already know. Nearly nine in ten social network users (89%) say they use the networks to stay in touch with friends, and 57% say they use it to make plans with friends. Under half (49%) use the sites to make new friends.

Surprisingly, those on social networks for professional purposes are not as common as you may have thought. Only 6% of adults use LinkedIn, the online social network dedicated to professional networking, but 72% use other social networks (50% use MySpace, 22% use Facebook) for both professional and personal networking purposes. The most interesting finding is that less than a third of social network users are using them for professional purposes, regardless of which site they use.

More Tidbits: Demographics

Some other findings confirm what we've heard before about social networks: MySpace users are more likely to be women, Hispanic, black, and have a high school education or some college experience. The median age is 27. Facebook users are more likely to be male and have a college degree. The median age there is 26. LinkedIn, however, tends to be comprised of more older, white men with a college degree and median age of 40. The prevalence of men on these networks could be explained by the fact that men are more likely than women to have two or more online profiles (54% vs. 47%).

What It All Means

It appears that the trend of using social networking sites for professional purposes is not quite as common as we may have thought. Although there are portions of the population both young and old that do so, it isn't the main reason people join social networks. It's more common for people to go online to use the networks as they were originally intended - to socialize. That's not a bad thing, we suppose, but it will be interesting to see what this means for sites like LinkedIn, whose main purpose is to cater to the professional crowd.

We've already seen LinkedIn attempt to expand their network in new ways not too long ago. Just this past year, we've watched as LinkedIn added LinkedIn applications, an effort to make their network more interesting and dynamic. They also added helpful features for business-minded folks like the events section, which debuted last November. But it was only a month ago that the company brought in a new CEO, or rather, an old one - the company founder Reid Hoffman. Perhaps that means LinkedIn is planning to shake up their site and make it more relevant and popular among online users than it is today.