New research revealed today suggests that social networks have caused a fundamental shift in the way people interact with each other and with media.

According to research by MySpace in partnership with Isobar and Carat USA, more than 70% of Americans 15-34 are actively using social networks online, and the research showed social networking sites taking a strong foothold in the primetime hours.

The study also found that more than 40% of all social networkers said they use social networking sites to learn more about brands or products that they like, and 28% said at some point a friend has recommended a brand or product to them.

Of those polled, 69% said they utilize social networks to connect with existing friends and 41% said they use the sites connect with family members.

In addition, the study revealed that current social networkers spend on average more than 7 hours per week on social networking sites, and that those hours are driving the growth of overall time spent online.

The results match a survey by Pew Internet at the beginning of the year which said that more than half (55%) of all online American youths ages 12-17 use online social networking sites.

The survey also finds that older teens, particularly girls, are more likely to use these sites. For girls, social networking sites are primarily places to reinforce pre-existing friendships; for boys, the networks also provide opportunities for flirting and making new friends.

However, a new report by Forrester Research which has grouped social network users into six categories based on their level of participation, suggests that over half, 52%, were "inactive" and didn’t frequent social networking sites at all.

Of the 48% that did visit social networking sites, 33% were classed as "spectators" choosing to watch podcasts, videos and read blogs but not to get involved. "Joiners", (19%) join social networking sites, "collectors" (15%) tagged websites and use RSS feeds and "critics" (19%) post ratings and leave comments on blogs.

The topmost level of participation is "creator" and comprised just 13% of respondents. Creators are akin to online publishers and regularly upload videos, maintain blogs, leave comments and add to the online content of social sites.