As theories circulate about the actual dollar value of sites like Facebook and Myspace-analysts recently placed Facebook's worth at $10 billion-there is no question that people continue to gravitate in droves towards social networking and blog sites. In the U.S. alone, total minutes spent on social networking sites has increased 83 percent year-over-year. In fact, total minutes spent on Facebook increased nearly 700 percent year-over-year, growing from 1.7 billion minutes in April 2008 to 13.9 billion in April 2009, making it the No. 1 social networking site when ranked by total minutes for the month.

"We have seen some very exciting growth in Facebook during the past year, and a subsequent decline in MySpace. Twitter has come on the scene in an explosive way perhaps changing the outlook for the entire space. The one thing that is clear about social networking is that regardless of how fast a site is growing, or a how big it is, it can quickly fall out of favor with consumers," said Jon Gibs, vice president, media and agency insights, Nielsen Online. "Remember Friendster? Remember when MySpace was an unbeatable force? Neither Facebook nor Twitter are immune. Consumers have shown that they are willing to pick up their networks and move them to another platform, seemingly at a moment's notice."

Top 10 Social Networking and Blog Sites Ranked by Total Minutes for April 2009 and Their Year-over-Year Percent Growth (U.S., Home and Work)

Myspace Visitors Love Videos--Make it No. 1 Social Networking Site when Ranked by Video Streams

While the popular consensus is that Facebook has become the top dog in the social networking space-April was the fourth month in a row that Facebook held the top spot in both unique visitors and total minutes-Myspace has been winning in one arena: online video. With 120.8 million video streams, Myspace.com was the No. 1 social networking destination when ranked by streams and total minutes spent viewing video. Myspace visitors spent 384 million minutes viewing video on the site, with an average of 38.8 minutes per viewer. In comparison, Facebook visitors spent only 113.5 million minutes viewing video in April, with an average of 11.2 minutes per video viewer.

So maybe the better questions to ask are whom does each site reach -- not who is "winning"  -- and what audiences are they drawing and how are they building for the future to maintain the loyalty of their visitors who to this point have shown little long-term loyalty to any specific platform.

In April 2009, visitors aged 25 to 34 and 35 to 49 were the highest indexing age groups on Facebook, being 27 percent and 23 percent more likely to visit the site than the average user, respectively. In contrast, the highest indexing demographics on Myspace.com was people aged 18 to 24 and 12 to 17.

Unique Audience Composition Index by Age Group for Facebook and Myspace.com in April 2009 (U.S., Home and Work)