Measuring ROI for Social Media Marketing

I recently ran across this article while I was looking for news related to social media marketing. I figured it might be helpful for the group project for members who will be working on the ROI section. Maybe it is just the natural skeptic in me but I do not really see how an increased number of comments one receives or the number of followers you have translates into a visible ROI. On the other hand I guess an increase in web traffic and positive or negative comments would help boost awareness of your product, which in turn could have a direct effect on sales.