For many marketers who were sitting on the sidelines of social networking as recently as four months ago, advertising on social networks has become a top priority.

In a recent interview with eMarketer, Michael Barrett, chief revenue officer at Fox Interactive Media (FIM), said, "The conversation with marketers has shifted in recent months from 'Why MySpace?' to 'How can I use MySpace?'"

"At this point, many of the dollars are still experimental, but in certain categories such as movies, TV and music, marketers are actively budgeting funds to social networking campaigns," says Debra Aho Williamson, eMarketer senior analyst and the author of the new Social Network Marketing: Ad Spending Update report. "Much like in the early days of Web marketing, there is a fear of being left behind: If a competitor is there, then I need to be there, too."

In fact, the pace of events since August (including Google's $900 million deal with MySpace and the trickle-down effects of this deal) has led eMarketer to revise its expectations for social network ad spending upward.

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