Remember last year's big news about the power of social connection: that friends could make you fatter, happier, and even sexier? Whether you're a believer or not, new data now says friends will make you visit websites that may make you any of the above.

According to analysis firm Compete, Facebook is now the top source of traffic to entertainment and news portals, besting even the ubiquitous Google. It may sound like just another data point in the ocean, but it hints that the good old days of search may be gone – replaced by the power of a person's social network to determine what sites are worth a visit.

"People are spending less time navigating the Internet on their own and are now navigating the Internet based on their friends' recommendations or their friends' activities," Dave Yovanno, chief executive of social media service company Gigya, told the San Francisco Chronicle. "That's one of the big trends we started picking up on probably four or five months ago."

Thirteen percent of Web traffic to major web portals such as Yahoo, MSN and AOL came from Facebook. Ebay was in second place, with 7.61 percent. And Google, which has made its fortune as a Web door porter-cum-concierge, placed third with 7 percent. (MySpace took fourth place, with just under two percent.)

Of course, the race to be the web's top source of referral traffic has been and is both closely watched and hotly contested, because every measurement firm (Compete is just one of many) has its own data and methodology. But the big picture appears to be consistent across all reports: Facebook is growing (currently it claims 400 million active members), as is its influence on Web traffic patterns.

"Friendcasting" is how experts are referring to the phenomenon of social networks determining the news stories we read and the videos we watch. It's changing online marketing. If your business depends on attracting more web traffic, consider this a sign that you should worry a little less about search engine optimization and a little more about developing your social-media strategy.

Jessica Ong, Compete's director of online media and search, told the San Francisco Chronicle: "The message for the advertising industry is that more serious attention needs to be paid to social-networking sites like Facebook, and advertisers need to figure out how to leverage this traffic."

David Berkowitz, director of emerging media and client strategy for New York digital marketing firm 360i, pointed to two signals last week from Google itself about social media's power. There was, of course, the launch of Google Buzz, which gives Gmail users the Facebook-like powers of posting updates, links, and photos. And there was the company's purchase of Aardvark, a company founded by former Googlers, which taps users' contacts to find someone to answer their questions.

The mobile web will grow into a fresh source for searches, Berkowitz adds – "but social media's just finding its feet and the business models are just starting to emerge. And they're evolving quickly."