No more than the web can make you dumb. The study was about what social news users choose to focus on. That's a choice that all web users make, and on balance

No more than the web can make you dumb. The study was about what social news users choose to focus on. That's a choice that all web users make, and on balance, most are probably better informed as a result. It's also quite possible that social news users get a lot of mainstream news, but just not at reddit or digg.