  A particular challenge in the area of social media analysis is how to find
communities within a larger network of social interactions. Here a community
may be a group of microblogging users who post content on a coherent topic, or
who are associated with a specific event or news story. Twitter provides the
ability to curate users into lists, corresponding to meaningful topics or
themes. Here we describe an approach for crowdsourcing the list building
efforts of many different Twitter users, in order to identify topical
communities. This approach involves the use of ensemble community finding to
produce stable groupings of user lists, and by extension, individual Twitter
users. We examine this approach in the context of a case study surrounding the
detection of communities on Twitter relating to the London 2012 Olympics.
