Hitwise has announced that one in 20 U.S. internet visits in September 2006 went to one of the top 20 social networking sites such as MySpace.com.

The company's report, "Hitwise US Consumer Generated Media Report," also found that visits to MySpace increased 51 percent March through September 2006.

"This report shows how influential the creation and consumption of user content has become as a web activity, and demonstrates its significance in driving web traffic to other categories," says LeeAnn Prescott, director of research at Hitwise and iMedia contributor. "The use of social networking, photo hosting and online video websites represent a significant shift in online user behavior, and Hitwise Clickstream data is particularly useful in understanding how these users are interacting with the web."

Last week fellow online research company eMarketer announced that ad spending on social networks will hit $2.15 billion by 2010.