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.

It wasn’t long ago when things were different. I still remember a few years back when I would ignore requests from others to connect on sites such as LinkedIn. Over a period of time, after repeatedly getting requests to connect from friends and acquaintances, I finally reached a tipping point and joined the network. The critical mass of users on the application, in addition to word-of-mouth recommendations, was good enough for me to see enough value to joining the network. Others had collectively convinced me to change my ways and join the application—this is one aspect of how collective intelligence is born and can manifest itself in your application.

Over the last few years, there’s been a quiet revolution in the way users interact. Time magazine even declared “you,” as in the collective set of users on the web, as the person of the year for 2006. Users are no longer shy about expressing themselves. This expression may be as simple as forwarding an interesting article to a friend, rating an item, or generating new content—commonly known as user-generated content (UGC). To harness this user revolution, a new breed of applications, commonly known as user-centric applications, are being developed. Putting the user at the center of the application, leveraging social networks, and UGC are the new paradigms, and a high degree of personalization is now becoming the norm.

It’s been almost two years since I first contacted Manning with the idea of writing a book on collective intelligence. Ever since my graduate school days, I’ve been fascinated by how you can discover interesting information by analyzing data. Over the years, I was able to ground a lot of theory in the practical world, especially in the context of large-scale web applications. One thing I knew was that there wasn’t a practical book that could guide a developer through the various aspects of applying intelligence in an application. I could see a typical developer’s eyes roll when delving into the inner workings of an algorithm or applying some of the collective intelligence features. There’s immense value that an application can create by leveraging user-interaction data. As more and more companies joined the Web 2.0 parade, I wanted to write a book that would guide developers to understanding and implementing collective intelligence–related features in their applications.

It took longer to write this book than I had hoped. Most of the book was written while I was working full-time in demanding jobs. But the experience obtained by implementing these concepts in the real world provided good insight into what would be useful to others.

Remember, applications that make use of every user interaction to improve the value of the application for the user and other potential future users, and harness the power of virality, will dominate their markets. This book provides a set of tools that you’ll need to leverage the information provided by the users on your site. Whatever forms of information may be available to you, this book will guide you in harnessing the potential of your information to personalize the site for your users. Focus on the user, and you shall succeed. For collective intelligence begins with a crowd of one.