"A lot of our evangelists are evangelists because they simply love the product," said Laurie Weisberg, a senior vice president of Informative, a word-of-mouth marketing firm. "They don't need to be rewarded with discounts or anything like that."

Loosely borrowing from Malcolm Gladwell's best-selling book "The Tipping Point," Ms. Weisberg lectured on the importance of using "influencers," or people who have large social networks and are good communicators, and "promoters," people who talk positively about a brand.

Word-of-mouth marketing makes it easier for people to do something they already do: share knowledge about new products so they can feel more important, said George Silverman, the author of "The Secrets of Word-of-Mouth Marketing."

"People engage in word of mouth because they want to look good," Mr. Silverman said. "Word of mouth is the most honest advertising medium there is. People don't want to hurt their friends and family and colleagues with bad information."

The importance of ethics and full disclosure was also a recurrent theme at the conference, as speakers repeatedly warned attendees not to misrepresent themselves when, for instance, pitching a product on an online message board. In other words, do not try to be stealthy, said Robert Ricci, the director of Web relations for Weber Shandwick, a public relations firm that is part of the Interpublic Group of Companies.

"If you're working on a video game, and you go onto a video gamer's blog, let your contacts know that you are an employee of said company," Mr. Ricci said while leading a session titled "How to Work with Bloggers and Communities, the Ethical Way." "Always let them know what your intentions are up front."

But replacing traditional advertising with word-of-mouth and viral marketing is an outlandish notion for most companies. A session devoted to integrating word-of-mouth marketing with traditional advertising drew a crowd, but the main lesson seemed to be how to persuade a C-list celebrity to market your product free. (In this case, the agency for Downy, the fabric softener from Procter & Gamble, enlisted Delilah Luke, a radio D.J., to rave about new Downy Wrinkle Releaser on the air.)