The widespread adoption of smartphones equipped with high-quality image-capturing capabilities coupled with the prevalent use of social networks have resulted in an explosive growth of social media content. People now routinely capture the scenes around them and instantly share the multimedia content with their friends over a variety of social networks. The social network functions also ensure that much of this content comes with some form of social annotations. This environment sets the stage for advances in large-scale media research. This special issue hopes to address these challenges. The articles in this issue cover identification of use cases and task design, dataset development, and basic research over existing datasets.