What if they gave no forecast and everybody came? That's more or less what happened Monday when the ad industry's top forecaster embarked on a sojourn deep into the heart and soul of social media, meeting with digital gurus in a series of "desk-side chats," popping into an industry social media conference, and interacting with the "community" throughout the day via Twitter posts and replies - all as he was being followed by a journalist who was simultaneously chronicling the whole affair via a live blog. The forecaster was Interpublic's Brian Wieser, and the journalist was this reporter, and the day resulted in some profound insights into the definition of the term "social media," whether it actually constitutes a new form of advertising, and if not, what its ultimate impact on the advertising industry might be. What the process did not yield, however, was an actual number for social media ad spending in the years to come. Like much of the world of social media, the process was disjointed, nonlinear, conversational, full of personal reflections about the state of media and how it is being transformed by a new array of tools, technologies and platforms all loosely assembled under the broad descriptor of social media. Along the way, Wieser spouted apocryphal, and seemingly prophetic quotations from his idol Marshall McLuhan during cab rides between meetings; got into heated debates about the meaning of social media, and its application to the advertising world; and expressed a personal dislike for the kind of short, insubstantial microblogging that has become all the rage in the social media industry. If you'd like to get some perspective on that portion of Monday's dialog, just mosey on over to Wieser's Twitter feed at http://twitter.com/brianwieser, or all of the replies associated with them at the #magnaforecast hash tag. Wieser said he embarked on the process, because, as McLuhan once noted, "the medium is the message," but also because it was probably the only way for him to really get a handle on what social media is, and how it could possibly be forecasted in traditional advertising terms. The process resulted in a working definition - actually a synthesis of a series of expert definitions for social media - that Interpublic plans to post on Wikipedia soon. (The current Wikipedia definition can be seen at http://en.wikipedia.org/wiki/Social_media). What it did not result in, is an actual monetary forecast, marking the first time Wieser has abandoned one of the main emerging media platforms since he began forecasting their advertising volume several years ago. Asked by Buddy Media's Michael Lazerow Monday afternoon for a preview of what Wieser's social media forecast would end up like, Wieser confided: "There are no numbers. This is the forecast. You are part of it." In his last emerging media forecast released in July 2008, Wieser predicted that spending on social media platforms, including social networks such as Facebook and MySpace, would grow 37.4% this year to $1.474 billion from $1.073 billion in 2008. In some of his recent forecasts for other emerging media platforms such as mobile, advanced TV, and online video, Wieser has downgraded his projections for the rate of growth this year due to the impact of the macro economy, but most remain at relatively high double-digit rates of growth. All the experts, including top Interpublic digital media mavens such as Bant Breen, Reprise Media's Josh Stylman, the Emerging Media Lab's Raquel Krouse, and Universal McCann's Brian Monahan, agreed that social media is having a significant transformational effect on the way consumers and marketers use media, but many did not see social media necessarily as a form of advertising in and of itself. Instead, it is viewed as a set of technologies, tools and platforms that advertisers, agencies, and users alike use to interact with, or without brands.