Here's a fresh snapshot of where and how much Americans are social networking. Hitwise just announced its latest figures, finding that - out of Hitwise's group of 53 leading social sites - MySpace averaged 76.35% of all US visits last year. Next came Facebook.com, Bebo.com and BlackPlanet.com with 12.57%, 1.24%, and .87% respectively. As for the number of visits in a single month (December), MySpace received 72% of them, Facebook 12.57% (with a 50% increase in traffic over December '06), and Bebo 1.09%. There were huge traffic gains outside the Top 3 too, though: MyYearbook.com, popular among teens and founded by teens, had the biggest "gain in market share" last month, Tekrati.com reports, with a whopping 407% increase over December 2006. Facebook and Disney's popular kids' "social network" increased 51% and 48%, respectively.