“We are trying to provide the antidote for the consumer rebellion against interruptive advertising,” says Sheryl Sandberg, Facebook’s chief operating officer and Mr. Zuckerberg’s business consigliere.

Ms. Sandberg, who ran Google’s highly successful advertising initiatives before leaving the search giant to join Facebook, said her company’s revenue was growing despite a brutal downturn that is hurting other kinds of online advertising. She also puts one rumor to rest, saying the company is not considering charging members for any aspect of its service.

“We’re pretty pleased with the overall trajectory,” she says. “Our conversations with big advertisers have broadened in scope and we also have more people asking about how they can work with us.”

Facebook recently introduced advertising tools to let companies focus on users based on the language they use on the site and their geographic location. So, for example, an advertiser can now tailor a message to the Latino community in Los Angeles or French speakers in Montreal.

Despite the gloom permeating much of the advertising world, and the formidable challenges facing the site, some advertisers say they glimpse the future in Facebook’s brand of interactive advertising.

“Our clients all want to see if they can make this work,” says Al Cadena, the interactive account director at Threshold Interactive in Los Angeles, which represents companies like Nestlé, Honda and Sony. “Advertising used to be a one-way communication from advertiser to consumer, but now people want to have a dialogue. And Facebook is becoming the default way to do that, not only in the States but really for the whole world.”

Internet evangelists say that when a technology diffuses into society, as Facebook appears to be doing, it has achieved “critical mass.” The sheer presence of all their friends, family and colleagues on Facebook creates potent ties between users and the site  ties that are hard to break even when people want to break them.