Advertisers are experimenting on Facebook, MySpace and niche social networks. In 2008, they are expected to spend $1.6 billion--a rise of 69% over the $920 million they spent in 2007, according to a new eMarketer report, Social Network Marketing: Ad Spending and Usage. eMarketer predicts that the total US social networking audience will grow by 46% over the next four years to 105 million in 2011. While the leading social networks, MySpace and Facebook, are now targeting ads based on members’ interests like word-of-mouth marketing, that ad technique will evolve and be joined by several other methods. In coming years, for example, advertising will appear not only on social networking destination sites but also within other internet activities, such as online shopping, e-mail, or search, which will take on social networking attributes.