Pretty much since the dawn of public relations, we’ve operated on the same principle as invading aliens. We land on a particular subject, look around and say “take me to your leader.” Sometimes that is a leading advocate or a journalist with extraordinary reach or some other investor, tastemaker or celebrity. For every tribe, the reasoning goes, you can find a chief.

But the power of this approach is fading as the Internet gives rise to a new kind of group: the loosely organized, leaderless organization. The last year has been full of examples of these collectives: the vigilante hackers of Anonymous, the (more or less) spontaneous Occupy movements. But the most wonderful example is what’s happening in health care. Patients and physicians and other stakeholders are leveraging the democratic nature of the web to build true communities.

Last week, USA Today profiled a group that is making the concept a reality. A small group of women, including Jody Schoger, Alicia Staley and Dr. Deanna Attai, has organized a weekly tweetchat on breast cancer social media (known by its hashtag: #BCSM). It’s less a support group than an extended family, not just sharing advice and experiences, but the joys and sadness of everyday life. There may be no truer picture of the experience of women living with breast cancer or breast cancer survivors than what goes down each Monday night on Twitter.

And it’s not just breast cancer. The most powerful force in diabetes today may not be the well-funded organizations that have long rallied support for the disease: it’s a loose, collection of bloggers that’s known informally as the “Diabetes Online Community” (DOC, for short). No one created the DOC. No one is in charge. There’s no organization. And yet the informal network has immense power. ¬†Ditto for doctors, too. My colleague Greg Matthews, in his rigorous evaluation of 1,400 Twitter-centric docs, found that connections between physicians is also happening outside of traditional communications channels.

But BCSM, DOC¬† and groups like them turn the “relations” part of “public relations” on its head. If you want to tap into that hive of information, you can’t just go to the group’s founders (though Jody, Alicia and Deanna are remarkable resources in their own right). You have to become a participant yourself. You have to watch the conversation unfold, soak in the different perspectives and understand how the fabric of the community is knit together.

Joining a community doesn’t always come naturally in communications. It requires a certain degree of vulnerability, a whole lot of transparency and the knowledge that really understanding a group requires a tremendous investment of time. That’s a high barrier to entry.

It’s a barrier that communicators will have to clear if they want to understand this new phenomenon of self-organized groups. Increasingly, top-down, bureaucracy-driven organizations are in peril, removed from grassroots supporters who no longer need a large organization to have an impact. To be sure, collectives of Twitter users won’t eliminate the need for large, groups working toward well-defined goals. But — increasingly — they’ll serve as the voice of the people. Will you be listening?