  Understanding user dynamics in online communities has become an active
research topic and can provide valuable insights for human behavior analysis
and community management. In this work, we investigate the "bandwagon fan"
phenomenon, a special case of user dynamics, to provide a large-scale
characterization of online fan loyalty in the context of professional sports
teams. We leverage the existing structure of NBA-related discussion forums on
Reddit, investigate the general bandwagon patterns, and trace the behavior of
bandwagon fans to capture latent behavioral characteristics. We observe that
better teams attract more bandwagon fans, but they do not necessarily come from
weak teams. Our analysis of bandwagon fan flow also shows different trends for
different teams, as the playoff season progresses. Furthermore, we compare
bandwagon users with non-bandwagon users in terms of their activity and
language usage. We find that bandwagon users write shorter comments but receive
better feedback, and use words that show less attachment to their affiliated
teams. Our observations allow for more effective identification of bandwagon
users and prediction of users' future bandwagon behavior in a season, as
demonstrated by the significant improvement over the baseline method in our
evaluation results.
