Social media is a young person’s domain, right? Don’t be so sure. New research shows that the single biggest age group on Facebook is actually 35-54 year-olds. Middle-aged users make up 28.2% of all Facebook accounts, compared to just 25.2% for 24-34 year-olds. Up through last January, Facebook was dominated by younger users, the survey finds, but now 61.5% of users are over the age of 25– quite a feat for a network that was originally aimed at college kids. Experts wonder if the site’s growing popularity with older users may eventually hurt the network, which owes much of its success to its youth appeal. Check out this and other excellent links we found while searching for your SmartBrief on Social Media.