FORTUNE -- To hear certain Twitter enthusiasts (or as many of them are otherwise known, Twitter obsessives) tell it, the microblogging platform represents the future of news. In some ways, Twitter is already the present of news, since most big news organizations and many journalists use it to disseminate their work and that of their peers. But that's not what the Twitter True Believers mean: They mean the platform itself is becoming a vehicle not only for sharing links to news stories, but also a primary source of news -- often reported by "citizen journalists," which usually just means witnesses to events who share real-time (and unverified) information in 140-character squibs.
In neither sense, however, is Twitter likely to become a powerhouse news platform, though along with Facebook (fb) and LinkedIn (lnkd) it certainly can help spread news stories around. A newly released study from the Pew Research Center shows just how tiny and unrepresentative the universe of Twitter users actually is. And the population of people who use Twitter to follow and share news is tinier and less representative still. That might explain why following journalists on Twitter often makes some of us feel like intruders into a particularly insular, clubby, nerdy world.
According to Pew, just 13% of American adults ever use Twitter at all. And just 3% of adults ever tweet or retweet news stories. Pew didn't say what percentage of those people look to Twitter to find original news (such as on-the-ground reports from war zones or disasters), possibly because the number is so small, it can't be measured.
The study found that the views of Twitter users rarely track with those of the general public, at least on national political issues and events. And there's no consistency: Sometimes Twitter users' reactions to events skew more conservative than those of the public at large, and sometimes they skew more liberal. "The lack of consistent correspondence between Twitter reaction and public opinion" Pew says, "is partly a reflection of the fact that those who get news on Twitter -- and particularly those who tweet news -- are very different demographically from the public."
And there are so few people who do that, it really doesn't much matter what they think. It would seem that in some ways, Twitter pretty much lives up to its stereotype: It's full of people, many of them kids, commenting on celebrity culture, sports, music, and reality TV, engaging in interpersonal drama, or sharing their own personal musings, mundane life events, and, sadly, racist or otherwise hateful nonsense.
None of which is to say that Twitter can't be incredibly useful for people who do choose to use it to keep up with the news, or who belong to a community of interest. It most certainly can be that -- it's just that for most people, it isn't, and likely won't ever be. The utility of Twitter as a news platform is powerful but narrow. Few people other than journalists and people working in a particular field (such as, say, finance) need to have a real-time stream of constantly updated news. Speed, brevity, and immediacy are the only real benefits to Twitter. When those benefits are required, they are very beneficial. Otherwise, they're actually drawbacks. It's simply easier, more comfortable, and more useful for most people to get their news from TV, the Web, or even newspapers.
It probably doesn't help that so many journalists and other news-spreaders fill Twitter up with seemingly every thought and opinion that passes through their heads; insist on "live-tweeting" speeches, hearings, product introductions, etc.; and engage in flamewars with each other. What everyday news consumer wants to endure any of that?