Author Dana Boyd, who has just written a book titled "It's Complicated: The Social Lives of Networked Teens," found that children today are reacting online largely to social changes that have taken place offline. They roam online in part because they cannot roam outside anymore.
Here's an interview with Dana Boyd by Nick Bilton of The New York Times' Bits column after she wrote the book. And an earlier interview which she was doing her research: Cracking Teenagers' Online Codes.