But Valente still believes that word-of-mouth marketing can work under the right conditions. He believes, for example, that significant market penetration must be achieved before word-of-mouth marketing can become effective. “Once adopters outnumber non-adopters, word-of-mouth provides a positive influence. So the trick really is to get to that point,” he says. “The key is to generate interpersonal communication — making it ‘sticky,’ making it emotive, or just making it different as many advertisers try to do.”

Given deeply entrenched consumer resistance to traditional marketing, there has recently been increased interest in the possibilities of word-of-mouth approaches. Word-of-mouth recommendations have been found to be especially effective, for example, in influencing the decisions consumers make about vacation destinations, restaurants, movies, cars, computer software, magazines, TV shows, retail stores, websites and investments.

Keller and Berry find that brands do not define the lifestyles of opinion leaders, nor do these individuals purchase brands to create self-image. But, says Berry, “brand names still count for something. The New York Times, The Wall Street Journal, CNN, CBS and NBC are brand names that people do put more credibility in than a bulletin board on the Internet or a viral email.” Most opinion leaders believe that brand value is worth paying extra for, but only if a brand really is better. And among influentials, brands are valued as conveniences that save time for more important things.

In order for a brand to become successful, Keller and Berry suggest, it must be associated with a meaningful product; for example, something that improves the quality of life, that connects to a passion or that contributes to causes or concerns that the opinion leaders care about. Driven by a consumer-first mindset and an appreciation of low prices; innovative, easy-to-use technology; and quality at a reasonable price, the authors’ opinion leaders have given thumbs up to Wal-Mart, Southwest Airlines, Microsoft, Home Depot, Nokia, Charles Schwab, Dell Computer, Starbucks and FedEx.

Although a number of successful marketing campaigns have used word-of-mouth strategies, few have used word-of-mouth techniques alone. But start-up company LinkedIn of California, is currently attempting to buck the trend of dot-com downsizing by just using word-of-mouth. Starting with an idea once proposed by Harvard psychologist Stanley Milgram that every American is linked to every other by no more than six degrees of separation, the company attempts to bring professionals into connection with well-connected peers with whom they are linked by no more than four degrees of separation (for example, an associate of an associate of an associate). By extending the subscriber’s personal network from several hundred to thousands of individuals, the company seeks to give them an edge in meeting their business goals.

Randall Frost a freelance writer based in Pleasanton, CA, is the author of the forthcoming book The Globalization of Trade. Other work has been published by the New England Financial Journal, CBSHealthWatch, Modern Drug Discovery, Outdoor California and Gale.