The fastest growing demographic for Facebook and other social media: Those age 50 and over, says a new report.

Social networking use among Internet users ages 50 and older nearly doubled—from 22 percent in April 2009 to 42 percent in May 2010, says a survey of over 2,250 U.S. adults from the Pew Research Center's Internet & American Life Project.

The figures were even higher for the oldest users: Usage among those over the age of 65 percent grew 100 percent, from 13 percent last year to 26 percent in May 2010.

"Young adults continue to be the heaviest users of social media, but their growth pales in comparison with recent gains made by older users," said the report's author, Mary Madden, a Pew senior research specialist. The percentage of social networking users age 18 to 29 rose from 76 percent to 86 percent, according to the report.

Why are older adults logging on? To keep in touch with family and friends, hunt for people from their past, and seek support for chronic illnesses.

Those age 50 and older are also taking to Twitter in increasing numbers. In 2009, just 5 percent of Internet users age 50 to 64 had used Twitter or another status update service, but now 11 percent say they use these tools.

The major roadblock to older people taking to life online? A lack of broadband.

The report said: "Even though older adults may be among the most resistant to broadband, there is evidence that once these users get a taste of high-speed access, they often come to rely on the Internet as an everyday utility in their lives."

Will Facebook's new users push out its core audience? A June study from online gaming site Roiworld found that 16 percent of younger users leaving Facebook did so because their parents had joined. Another 14 percent left because they thought there were too many older people using the site.

In a bet that college-aged users want a return to the old days of Facebook – i.e. no parents or potential employers friending them – CollegeOnly.com launched last week. The site – started by New York-based entrepreneur Josh Weinstein -- is limited to people with an .edu email address. It's currently serving students from Yale, Cornell, and Weinstein's alma mater, Princeton,  and has already received requests from students around the world. Its investors include PayPal co-founder Peter Thiel.