- Adweek Staff

NEW YORK On a worldwide basis, marketers will spend an estimated $2.3 billion on social network advertising in 2009, eMarketer forecasts. In 2013, spending will reach an estimated $3.5 billion.   

Social network ad spending is taking a hit from the worldwide economic crisis and the ongoing challenge to develop effective ad models. Though a double-digit increase during a recession is still a good sign, eMarketer's previous growth-rate projection has been cut in half.

Key themes for 2009 include the rapid rise of social networking as a consumer activity around the globe; the potential for Facebook to become the dominant network in multiple markets worldwide; and the urgent need for sites to develop alternate revenue streams beyond advertising.