John Swift, who heads North American media buying for Omnicom Media Group, one of the world’s largest purchasers of advertising, said that Facebook won’t replace TV anytime soon, but it offers a flexible canvas to reach consumers. “You’re not going to Facebook to watch a show,” he said. “But Facebook offers the unique combination that you don’t really see in a lot of digital platforms of amazing scale as well as a very personal engagement opportunity.”

Both Facebook and marketers have strong reason to explore its potential.

Consumer brands, from the beer giant Budweiser to start-ups like the clothier Trunk Club, want to reach people where they are spending their time. More and more, that place is Facebook. In June, the social network accounted for about one of every six minutes that Americans spent online, and one of every five minutes on mobile phones, according to comScore, a research company. Mothers, the typical household’s chief buyer of consumer products, are among the most dedicated users, spending nearly four times as many minutes on Facebook as other people.

Marketers are starting to become believers in the value of Facebook, shifting more of their budgets to the service from other media channels, especially print and direct mail. The company just reported unexpectedly strong growth in revenue and profits for the second quarter, prompting investors to send its stock to record highs.

Image Sticky notes kept track of different ideas. Credit... Michael Falco for The New York Times

Still, Facebook has changed its pitch and the products it offers advertisers so often that many marketing executives are wary. A few years ago, the company was telling brands to increase the number of people following their pages. Now it says fans are largely irrelevant. Until late last year, it was promoting the power of ads in which people’s likes and comments about a brand were turned into endorsements sent to their friends. After legions of user complaints — and a class-action lawsuit — Facebook switched gears again. Now it boasts about its ability to pinpoint potential customers on their cellphones and Facebook.com based on its data about them. The company’s newest offering uses those profiles to serve targeted ads inside other companies’ mobile apps. Facebook is also pushing new video ads that would compete with TV for marketing big events, like movie openings.

Given the social network’s constantly changing messages, it was no wonder Mr. Rodrigues was annoyed. He had come to Facebook for its promise of precise ad targeting.

“We go against fish oil users,” he declared at the brainstorming meeting, meaning he wanted the ads to appear on the news feeds of those users. “We go against people who have heart concerns.” Several other R.B. managers chimed in their support.