Atthelevelofpopulationscale,socialmediaoffersusarich opportunity. People blog. They join groups, they comment on blogs.Otherscommentontheirblogs.Theyfollowgroups,stay or leave them. Interestingly, they are willing to tell others how they feel! This media offers a rich opportunity to explore the relation between social capital and critical aspects of mental well-being—mood and mood swings. Are moods different for groups with different levels of social connectedness? What are themaincomponents,latentfactorsofmoodswing?Essentially, how good a sensor is social media for social capital’s connectiontomoodandwell-being?Wedefineonlinesocialcapitalin online communities. Continuing with the core components of