Preface

“What is the virality coefficient for your application?”

This is an increasingly common question being asked of young companies as they try to raise money from venture capitalists. New products are being designed that inherently take advantage of virality within the product. Companies such as YouTube, Facebook, Ning, LinkedIn, Skype, and more have grown from zero to millions of users by leveraging the power of virality. With little or no marketing, these types of companies rely on the wisdom of crowds to spread exponentially from one user to two users, then four, then eight, and so on. A simple link in an email, which worked for Hotmail to grow its user base, may no longer be adequate for your application. Facebook and LinkedIn enable users to build their networks by sending an invitation to others to connect as friends or connections; other applications such as Skype and Jaxtr provide free services as long as you’re connecting to someone who’s already a member, thus encouraging users to register.