According to a new report from eMarketer, paid advertising on social networks in the US will drop 3% in 2009. In 2008, advertisers spent $1.175 billion on ads on social networks, but eMarketer predicts that this number will fall to $1.14 billion this year. The main culprit here is MySpace. EMarketer expects that ad spending on the social network will fall 15% in 2009. At the same time, it expects to see a 9% growth in ad spending on Facebook, and most other social networks are also doing just fine. EMarketer expects that this drop will be short-lived, however, and predicts a 13.2% increase in ad spending in 2010.