How much time do kids spend on line and what are they doing?

Social media use has become so pervasive in the lives of American teens that having a presence on a social network site is almost synonymous with being online. Fully 95% of all teens ages 12-17 are now online and 80% of those online teens are users of social media sites. Many log on daily to their social network pages and these have become spaces where much of the social activity of teen life is echoed and amplified—in both good and bad ways.

http://pewinternet.org/Reports/2011/Teens-and-social-media/Summary/Findings.aspx