Here Comes Everybody.
In his forthcoming book, Clay Shirky explains how internet media has become social media - allowing customers to follow their natural instincts and act in groups.
The book does not fully detail the implications for business but elsewhere he nails it,
What do businesses need to know: Businesses need to know that the old simplicities of dealing with their customers are disappearing, because customers are now able to coordinate their actions in groups......Now, thanks to social media, customers are part of active groups, groups that form and dissolve quickly in response to people's interests or needs -- most messages in this media flow within social groups, rather than from businesses to individuals.
If your marketing outlook doesn't fully embrace that simple fact, it's operating in a world that is fast disappearing.