There are many open problems in the area of diffusion in social networks. First, we believe that data-driven approaches, such as those described in the Chap. 7, are really still in the early stages of development. We have noted that recent work of this type deals with issues such as predicting the influence of individuals nodes, predicting the outcome of a diffusion process, and identifying more realistic models. Work in this area spans from observational studies in disciplines such as sociology and economics to the machine learning approaches seen in the computer science community. As data on real-world diffusion traces become more available, we expect this line of work to grow further.