David Hahn has spotted a trend. As director of advertising for the popular online business networking site LinkedIn, he's being asked pointed questions by large advertisers about his ability to help them find "influentials" -- those people within the LinkedIn community who are the most likely to go out and spread the word about a particular product or experience. "Some of them are requesting it specifically, while others are more implying it, but it comes down to the same thing," Hahn said. "Marketers are very interested in the value of online social networks, and how leaders in those networks can be used to drive proactive behaviors in the population."

Hahn isn't alone in his observations. "The notion of the online influencer is quite the thing today in the marketing world," said Janet Edan-Harris, CEO of Umbria, which monitors chatter in cyberspace communities for corporations wanting to know what's being discussed online about their brands and products. "Companies are incredibly eager to get to those people. Do that -- or so the conventional wisdom says -- and you'll be in marketing heaven."

But new research, as well as growing business experience, suggests that such thinking may be overly simplistic. The effectiveness of using online word-of-mouth campaigns -- or using individuals rather than traditional media advertising to spread the word about products or services -- is increasingly viewed as an effective way to reach consumers. But the popular notion that frequently accompanies this, that there are special individuals who hold the key to the hearts of entire online communities, is coming under fire.

Dave Balter certainly thinks so. As CEO of BzzAgent, a word-of-mouth marketing firm, Balter three years ago had a revelation: The so-called influentials, or opinion leaders, in online communities can't be influenced in a way that accelerates the success of a word-of-mouth campaign.

"We actually believed in the idea that influentials drove market trends at that point," said Balter. "But upon closer look, we found out it didn't add up. The sales data of our campaigns didn't match the profiles of the opinion leaders we had targeted, and it really caused us to re-evaluate some of our core assumptions." Today, when a client comes in with the goal of influencing the influentials, "we tell them that's fools' gold," says Balter. "It sounds really great, it sounds really sexy, but the results simply don't fly."

Duncan J. Watts, professor of sociology at Columbia University who studies networked communities, recently conducted research that indicates there is no hard evidence that the long-held belief in opinion leaders as, well, leaders, has any basis in fact.

This indeed is what Edan-Harris has concluded from her experiences working with online communities. "We said, 'Wait a minute, is this really a correct assumption, that there are individuals on the Internet that have that much influence?" she said. Her conclusion: "Not nearly as much as everyone seems to think."

Despite this, companies are putting significant dollars into efforts to find these online opinion leaders, whether they're bloggers, contributors to discussion boards, or members of online social networks. Indeed, a whole cottage industry has sprung up based upon the notion that all marketers need to kick off a successful marketing strategy with a list of Internet opinion leaders. Yet Watts calls much of the current thinking on this topic "sloppy." "This is a very simplistic notion, that there are magic people out there, and if I can just turn them on, I've got it made," he said.