Social networks continue to draw in millions of users, but advertising has not kept pace. EMarketer estimates total social network ad spending in the U.S. will fall 3% to $1.1 billion in 2009 from $1.2 billion in 2008. This is a significant turnaround from previous years, when spending grew an estimated 33% in 2008 and 129% in 2007. The primary reason for the change is a projected fall-off in ad spending on MySpace, which accounts for nearly one-half of U.S. social network ad spending. The challenges facing MySpace do not necessarily mean other companies operating in the social network space will face similar problems. Facebook, for example, is expected to increase its U.S. ad revenues, and U.S. ad spending on widgets and applications is projected to increase as well. To find out more about digital marketing and social network ad spend estimates from eMarketer click here.