A number of technology products display positive network effects, and are used in variable quantities by heterogeneous customers. Examples include operating systems, infrastructure and back-end software, web services and networking equipment. This paper studies optimal nonlinear pricing for such products, under incomplete information, and with the threat of competitive entry. Both homogeneous and heterogeneous network effects are modeled. Conditions under which a fulfilled-expectations contract exists and is unique are established. While network effects generally raise price, it is shown that accompanying changes in consumption depend on the nature of the network effects - in some cases, it is optimal for the monopolist to induce no changes...