A few of us have been saying this for some time, so it's good to see that Meeyoung Cha's research backs us up! From Scott Berinato on Harvard Business Review:
Cha called her paper, "The Million Follower Fallacy," a term that comes from work by Adi Avnit. Avnit posited that the number of followers of a Tweeter is largely meaningless, and Cha, after looking at data from all 52 million Twitter accounts (and, more closely, at the 6 million "active users") seems to have proven Avnit right. "Popular users who have a high indegree [number of followers] are not necessarily influential in terms of spawning retweets or mentions," she writes.
Berinato's interview with Cha in that post is also very interesting, and whilst some of her conclusions might just be confirming our existing gut feelings, it is very good to have some proper evidence upon which we can build.
Reading the comments to Berinato's piece, however, leads me to think that some people are misinterpreting Cha's conclusions. She's not saying that social media has no use, she's saying that follower numbers are not the right metric to measure influence (just like traffic stats for blogs don't always correlate to their influence). The baby should not be thrown out with the bathwater.