A 2011 study by Yahoo Research, shows that a small population of bloggers, media, celebrities, and organizations dominate the open discourse on Twitter:
Shaomei Wu, Winter Mason, Jake Hofman, Duncan Watts, Who Says What To Whom On Twitter
“Who Listens To Whom”
The results of the previous section provide qualified support for the conventional wisdom that audiences have become increasingly fragmented. Clearly, ordinary users on Twitter are receiving their information from many thousands of distinct sources, most of which are not traditional media organizations—even though media outlets are by far the most active users on Twitter, only about 15% of tweets received by ordinary users are received directly from the media. Equally interesting, however, is that in spite of this fragmentation, it remains the case that 20K elite users, comprising less than 0.05% of the user population, attract almost 50% of all attention within Twitter. Thus, while attention that was formerly restricted to mass media channels is now shared amongst other “elites”, information flows have not become egalitarian by any means.
The prominence of elite users also raises the question of how these different categories listen to each other. To address this issue, we compute the volume of tweets exchanged between elite categories. Specifically, Figure 3 shows the average percentage of tweets that category i receives from category j (indicated by edge thickness), exhibiting noticeable homophily with respect to attention: celebrities overwhelmingly pay attention to other celebrities, media actors pay attention to other media actors, and so on. The one slight exception to this rule is that organizations pay more attention to bloggers than to themselves. In general, in fact, attention paid by organizations is more evenly distributed across categories than for any other category.
Figure 3, it should be noted, shows only how many URLs are received by category i from category j, a particularly weak measure of attention for the simple reason that many tweets go unread. A stronger measure of attention, therefore, is to consider instead only those URLs introduced by category i that are subsequently retweeted by category j. Figure 4 shows how much information originating from each category is retweeted by other categories. As with our previous measure of attention, retweeting is strongly homophilous among elite categories; however, bloggers are disproportionately responsible for retweeting URLs originated by all categories, issuing 93 retweets per person, compared to only 1.1 retweets per person for ordinary users. This result therefore reflects the conventional characterization of bloggers as recyclers and filters of information. Interestingly, however, we also note that the total number of URLs retweeted by bloggers (465k) is vastly outweighed by the number retweeted by ordinary users (46M); thus in spite of the much greater percapita activity, their overall impact is still relatively small.
Although in a study like this — which does not actually track cascades — that conclusion is simply arithmetic, and could be wildly wrong, I think. In other words, bloggers might have a larger than arithmetic effect if their tweets lead to non-elite Twitter users to retweet their posts. I bet that is the case, too.