The Most Popular Social Network: Facebook

Facebook is by far the most popular social network, according to Brand Keys's newest Customer Loyalty Index, released Monday.

According to the annual list, which includes social-media sites for the first time, closely held Facebook bested other social-media sites, including News Corp.'s (NWS) MySpace, LinkedIn, Flickr and Twitter.

Facebook has more than 500 million users worldwide, putting MySpace in "a distant second," Brand Keys President Robert Passikoff told InformationWeek. Additionally, Flickr scored well because it solely specializes in photo sharing, while LinkedIn gained points on its ease of connection, Passikoff said.

In December, Facebook generated about 154 million unique users, making it that month's fourth most popular U.S. site after Yahoo (YHOO), Google (GOOG) and Microsoft (MSFT), ComScore said late last month. The company is a partner in a $250 million fund -- run by venture-capital firm Kleiner Perkins Caufield & Byers -- that launched last October to support new social-media applications and services.

Meanwhile, MySpace parent News Corp. last week said that it may sell MySpace. The company took a $275 million pre-tax charge, during the quarter ended Dec. 31, partly because of restructuring at the social network.