Social media services are complex ecosystems of human and technology where the user engagement and the infrastructure support need to be in balance. Sustainability of social media fundamentally depends on the ability to instigate and maintain the user engagement over time and develop business models that leverage that engagement to support the underlying technology. Thus, it is of paramount importance to develop techniques and metrics to monitor the health of the community and to adopt business models that are effective yet compatible with the users’ expectations and established trust. In this presentation we discuss the design challenges of social media, the tools for network analysis, and the implications of the advertising business models for user privacy.