Book excerpt: You read a book, you recommend it to a friend. That friend tells another friend. And another... until the book becomes this year's word-of-mouth sensation. This is the first to analyze the power of the 'pass-it-on' phenomenon, introducing us to the architects of the mightily efficient, money-spinning model known as the Viral Loop - the secret behind some of the most successful businesses in recent history. Outfits such as Google, eBay, Flickr and Facebook all employ the model at their core; all have seen their stock valuations skyrocket within years of forming. The genius lies in the model's reliance on replication: what's the point of using Facebook if none of your friends can see your profile, or using Flickr if you can't share your photos? Where's the joy in posting a video on YouTube if no one watches it? In creating a viral product that people want, need and desire, growth can, and will, take care of itself. Find out why the Loop will catch us all up, sooner rather than later...