It's practically impossible to overlook the impact blogs have made on PR. But even as tech advances, many potential influencers continue to rely on online message boards for dynamic peer-to-peer support, discussion, and debate.

One of the Web's most active message-board communities revolves around healthcare; groups comprising patients, medical providers, and even investors gather interactively to discuss a range of topics. For a PR pro, that means almost immediate feedback.

"There's a community for virtually every healthcare topic," says Ame Wadler, chair ...