U.S. adults ages 50 and up who use the Internet are flocking to social networks, according to the results of a survey of 2,252 adults ages 18+ by Princeton Survey Research Associates on behalf of the Pew Internet & American Life Project. The survey provides more evidence suggesting social media could become an effective advertising and marketing platform for reaching older Internet users (chronic offense-takers, please note that I did not write "old people"). The Pew findings are pretty dramatic: Among Internet users ages 50+ overall, social network use increased from 22% in April 2009 to 42% in May 2010. To boot, 10% of the 50+ cohort uses Twitter or a similar "status update" service, either to post updates or check other people's updates. Looking at specific age cohorts, social network use among Internet users ages 50-64 surged from 25% to 47%, with 20% of this group saying they check into social networks on a daily basis -- up from 10% last year. Meanwhile the proportion of Internet users ages 65+ using social networks doubled from 13% to 26% over this period, with the number checking in daily jumping from 4% to 13%. By contrast, social network use among Internet users ages 18-29 appears to be reaching saturation, growing from 76% in April 2009 to 86% in May 2010. These findings seem to jibe with some other figures I wrote about recently, suggesting that the overall rate of growth in social networks is slowing, but that growth could continue if social networks penetrate certain under-utilizing parts of the population -- especially older adults. The pool of potential users is growing rapidly: a separate study from Pew found that the proportion of Americans ages 70-75 who were online increased from 26% in 2005 to 45% in 2009.