(1) The Cardiff Online Social Media Observartory (COSMOS) aims to evaluate the challenges of using social media data in social research through developing tools to harvest, index, and analyze social media data. (2) One objective is to analyze social media data to monitor social cohesion and tension around events. This will examine measures of connectivity and sentiment related to social cohesion. (3) The implications of COSMOS include that it could be a surrogate for traditional methods, an augmentation through "mashing" social media with other data, or lead to a reorientation of methods through networked research and new populations. However, issues around statistical robustness, ethics, and surveillance need consideration.