The black-clad guests exuded cool as they sipped fruit-colored firewater from long-stemmed glasses. These lawyers, doctors, club owners and restaurateurs in their 20s and 30s were especially invited to 32º nightclub to taste Türi, a new vodka distributed by Bacardi. On this fall night, Türi was nothing more than an unknown vodka the bartenders were mixing in apple martinis, or with cranberry juice or Red Bull. But the hope is that these vodka drinkers will tell their friends about it, and they will tell their friends, and Türi will be the next Ketel One or Stoli.

"If we get it in the hands of the right people," the promoter said, "it can be a success. We just have to get it out there." This is the world of viral marketing, where word of mouth can be more influential than an advertisement, products catch on through casual chitchat, and everyday people act as marketing agents in exchange for products, cash or cachet. Viral marketers introduce consumers to products where they may least expect it. They hit them up in Internet chat rooms to talk about movies, stop shoppers in malls to hand them free gadgets, and give them alcohol in bars to get people talking.

Word of mouth used to happen naturally. Hush Puppies grew big again in the late 1990s because of buzz. And 50 Cent's Get Rich or Die Trying became an underground sensation long before it hit the pop charts.

But today, it is being staged. For example, Reebok has hired a "street squad" to wear 50 Cent's new G-unit sneakers in barbershops, hair salons and nightclubs throughout the country.

Marketing experts warn that while viral marketing techniques move fashion and image products - alcohol, energy drinks, cigarettes, candy - the strategy may backfire if young people realize they are playing into the hands of "the man."

"Stealth marketing walks a very dangerous line," said David Morrison, president of TWENTYSOMETHING Inc., a Philadelphia marketing-research firm. "If it's done correctly, you can make a legitimate connection with the target audience and break through the clutter," Morrison said. "If not done well, you will [alienate] the market; the method of communication will have backfired and you will damage the brand."

It also has the power to erode the public's trust, Morrison warns. Eventually, folks will be less open to conversations with strangers if they sense that their newfound friend is trying to ease into their pockets.