48% of Americans over the age of 11 now have profiles on at least one social networking Web site, including 78% of teenagers, according to a newly released study. In a study released today, The Infinite Dial 2010: Digital Platforms and the Future of Radio, research firms Arbitron and Edison Research said that the usage of social networking sites has doubled in just 2 years. In a similar study from 2008, it was reported that only 24% of Americans had a social media profile. In 2009, the study showed that 18% those with profiles checked them "several times a day." Today, that number is 30%. Broken down into age groups, as expected the number of people with social profiles decreases as the age demo goes up, but not dramatically. The following shows age groups and the percentage from that age group that have social profiles: - Teenagers: 78% - 18 to 24 years old: 77% - 25 to 34 years old: 65% - 35 to 44 years old: 51% The research firms did not note how many people over 45 have a social networking account. "Social networking has become a part of mainstream media behavior," said Edison's vice president of strategy and marketing Tom Webster. The study, which included surveys from over 1,750 people, also looked into other tech trends and found results such as: nearly 25% of Americans has used a MP3-player car adapter, 30% are interested in Internet Radio for their car, and 60% have a Wi-Fi network at home.