Due to developing technologies that are now readily available, user generated content (UGC) is growing rapidly and becoming one of the most prevalent and dynamic sources of information on the Web. Increasingly, more data appears online representing human judgment and interpretation about almost every aspect of the world: discussions, news, comments, and other forms of “socializing” on the Web. The increasing availability of such UGC from heterogeneous sources resembles a terra incognita of data and drives the need for advanced information retrieval (IR) technology that enables humans to search and retrieve it, navigate through it, and make sense of it. As such, UGC crosses paths with information retrieval (IR): it creates new IR scenarios, needs, and expectations.