In fact, Bitcoin is a four-sided network effect. There are four constituencies that participate in expanding the value of Bitcoin as a consequence of their own self-interested participation. Those constituencies are (1) consumers who pay with Bitcoin, (2) merchants who accept Bitcoin, (3) “miners” who run the computers that process and validate all the transactions and enable the distributed trust network to exist, and (4) developers and entrepreneurs who are building new products and services with and on top of Bitcoin.”