Putting more money into social media marketing

Borrell expects eightfold increase by 2015

The amount U.S. companies spend marketing themselves on social networking sites like Facebook is expected to grow from an estimated $4.5 billion last year to nearly $38 billion by 2015, according to a new report from Borrell Associates Inc.

More than 1.5 million local businesses participate in social networks, and they accounted for about half of all spending on social-networkmarketing last year, the report said.

"Given their unique ability to move messages among connected users, social networks have been irresistible to marketers looking for ways to deliver advertising and promotional messages," the report said. "The results to date have been breathtaking."