WebProNews

If MySpace were to lose its top spot among social networks, it'd have a long way to fall. Though US visits to the powerhouse were down five percent since last year, MySpace still commanded nearly 74% of the social networking market, according to Hitwise. 

Facebook, long in second place but up 32%, pulled in nearly 15% of US social networkers, a share that towers over its nearest competitor's.

That nearest competitor is one may not have heard of, but in the past year it has seen meteoric growth to grab a market share greater than Bebo, the traditional third place network recently acquired by AOL. MyYearbook.com grew by 475% to claim 1.33% of the US market, compared to Bebo's 1.09 percent.

On its homepage, MyYearbook boasts just over 66,000 members, but 15,000-plus signed up just today.

The numbers show not only how the third-place spot is pretty much up for grabs by a spry newcomer, but also that there may be a ceiling set in place by both Facebook and MySpace. And if MySpace loses another 5% next year, that's some trickle-down dominance available to just about anybody.

Though the entire social networking category is down 16% over all, Hitwise research director Heather Dougherty says loyal networkers are speding more time at them. "The growing number of applications and amount of content available for social networks are driving higher average visit times for the category, providing marketers with additional opportunities to reach these active users."