6.1 Introduction

Network effects are sometimes referred to as “Metcalfe’s Law” or “Network Externalities.” But don’t let the dull names fool you—this concept is rocket fuel for technology firms. Bill Gates leveraged network effects to turn Windows and Office into virtual monopolies and in the process became the wealthiest man in America. Mark Zuckerberg of Facebook, Pierre Omidyar of eBay, Caterina Fake and Stewart Butterfield of Flickr, Kevin Rose of Digg, Evan Williams and Biz Stone of Twitter, Chris DeWolfe and Tom Anderson—the MySpace guys—all of these entrepreneurs have built massive user bases by leveraging the concept. When network effects are present, the value of a product or service increases as the number of users grows. Simply, more users = more value. Of course, most products aren’t subject to network effects—you probably don’t care if someone wears the same socks, uses the same pancake syrup, or buys the same trash bags as you. But when network effects are present they’re among the most important reasons you’ll pick one product or service over another. You may care very much, for example, if others are part of your social network, if your video game console is popular, if the Wikipedia article you’re referencing has had prior readers. And all those folks who bought HD DVD players sure were bummed when the rest of the world declared Blu-ray the winner. In each of these examples, network effects are at work.