Facebook today introduced a new advertising initiative that allows businesses to target ads to the social-networking site's users based on their profiles.

The new ad initiative, known as Facebook Ads, represents an ambitious attempt by Facebook to monetize the 50 million people who have joined the site—and who have listed preferences in such categories as books, movies, and music.

"Facebook Ads represent a completely new way of advertising online," Facebook's chief executive, Mark Zuckerberg, told 250 marketing and advertising executives assembled at Loft Eleven in the Hell's Kitchen neighborhood of Manhattan.

"For the last hundred years media has been pushed out to people, but now marketers are going to be a part of the conversation. And they're going to do this by using the social graph in the same way our users do."

Flanked by representatives from Sony, Microsoft, and Blockbuster, Zuckerberg told the audience that more than 60 major consumer and Internet brands have signed on to the initiative. He announced that 100,000 new Facebook pages have been started, covering the world's largest brands, local businesses, organizations, and bands.

"The core of every user's experience on Facebook is their page and that's where businesses are going to start as well," explained Zuckerberg. "The first thing businesses can do is design a page to craft the exact experience they want people to see."

The idea is that advertising messages will be distributed virally through Facebook's social network. In essence, Facebook's own users will become viral marketers.

"Social actions are powerful because they act as trusted referrals and reinforce the fact that people influence people," said Zuckerberg. "It's no longer just about messages that are broadcasted out by companies, but increasingly about information that is shared between friends. So we set out to use these social actions to build a new kind of ad system."

Jeremiah Owyang a social media analyst with Forrester Research, said that Facebook's ad strategy heralds the arrival of the "fansumer," a combination of groupie and consumer.

"As consumers share their affinities, brands can advertise using trusted social relationships," Owyang said. "The traditional marketing funnel as we know it is distorted; endorsements are now passed from trusted customers to prospects, not direct from the brands themselves."

Given that vast amount of individual preferences stored in Facebook's database of users, Facebook Ads represents a potential gold mine for advertisers. As internet entrepreneur and recent celebrity dancer  Mark Cuban has pointed out, Facebook serves as a kind of individual billboard for millions of people, who input all kinds of data into the system.

"The data that is available about me [on Facebook] is the most comprehensive, self maintained database record about me on the internet or probably anywhere," Cuban wrote recently on his blog. "Access to that information times the however many tens of millions of Facebook active users is worth a lot of money."

Facebook said the system will serve ads "that combine social actions from your friends—such as a purchase of a product or review of a restaurant—with an advertiser's message. This enables advertisers to deliver more tailored and relevant ads to Facebook users that now include information from their friends so they can make more informed decisions."