(These) are economic networks having two distinct user groups that provide each other with network benefits. Example markets include credit cards,
composed of cardholders and merchants; HMOs; operating systems, travel reservation services; yellow pages; video games; and communication networks, such as the Internet. Benefits to each group exhibit demand economies of scale. Consumers, for example, prefer credit cards honored by more merchants, while merchants prefer cards carried by more consumers.
In (These), members of each group exhibit a preference regarding the number of users in the other group. Each group's members may also have preferences
regarding the number of users in their own group. A key feature of (These) is the novel pricing strategies and business models they employ. In order to attract one group of users, the network sponsor may subsidize the other group of users. Historically, for example, Adobe's PDF did not succeed until Adobe priced the PDF reader at zero, substantially increasing sales of PDF writers. Relative to Apple computer's initial pricing, Microsoft also steeply discounted SDKs leading to more rapid development of applications for MS Windows.