"Twitter is a goldmine," Rumford raved, speaking at the inaugural Gravity Summit on Social Media at UCLA Wednesday. He added that a number of big consumer brands are already on the site, such as Starbucks, which currently boasts about 6 million members.

Rumford also noted that small businesses are using Twitter to advertise, citing the example of a gourmet Korean taco truck business in Los Angeles. Since its launch in November, it has built a following through Twitter. "The driver tweets where the truck will be 20 minutes ahead of time, and literally hundreds of people show up," one conference attendee confirmed.

Marketers can use Twitter actively or passively, Rumford says, either by reaching out with promotional messages or setting up a "listening engine" that lets them track consumer sentiment in public postings on the site. Any active marketing must be handled carefully to avoid alienating consumers with the appearance of dishonesty or inauthentic, impersonal messages. "It's not a campaign," he advises, "it's a conversation."

As with blogs, Rumford conceded that "people are going to be saying bad stuff about your brand, and that's OK." He says negative comments can be an opportunity for customer-service intervention.

Yet companies are still mishandling this kind of functionality, Rumford says. He cited Motrin's slow reaction to widespread criticism on Twitter about an ad featuring pregnant women that was seen as misogynist.

On the upside, Rumford said efforts to drive people to particular online destinations can be tracked and measured by Google Analytics. Google also crawls and indexes all the conversation streams on the site.

Justin Goldsborough, social-media manager for Sprint, said the company uses Twitter to track consumer sentiment and customer service. But Sprint also uses Twitter and a corporate blog to coordinate business-related activities, says Goldsborough, who noted the site's growing penetration in all areas of American business.

"Retail employees are on Twitter," prompting some concern among management, but Goldsborough pointed out that it can connect these workers more closely to both customers and bosses. He cited BestBuy, which has a communal blog and chat site used by thousands of employees.

Online social media can be a highly effective advertising medium, but there are some pitfalls that can seriously damage a brand, the speakers warned conference attendees. All the presenters stressed the importance of honesty and transparency in Web marketing that relies on word-of-mouth.

David Reis, the founder and CEO of DEI, an online word-of-mouth marketing company, recalled the condemnation heaped on Belkin, an electronics manufacturer, for paying users $0.65 per post to write favorable reviews of its products on Amazon.com. "Basically, it's a simple problem: They lied," Reis said, emphasizing that marketers should always be forthright about their identities and mission.