The increasing mobile data demand and the proliferation of advanced handheld devices place user-provided networks in a conspicuous position for next-generation network architectures. There has been growing consensus that user-provided networks can play a crucial role in both self-organizing and operator-controlled wireless networks, as they enable the exploitation of the diverse communication needs and resources of different users. However, in user-provided networks both the availability of and demand for Internet access depend on mobile devices; therefore, the success of such networks relies on active user participation. In this article, we analyze the design challenges of incentive mechanisms for encouraging user engagement in user-provided networks. Motivated by recently launched business models, we focus on mobile user-provided networks where the energy consumption and data usage costs are critical and have a large impact on users' decisions on both requesting and offering user-provided network services. We outline two novel incentive schemes that have been proposed for such user-provided networks, and discuss the open issues that must be further addressed.