With the trend of user-community-based Web 2.0 applications, the circle related to library information have great concern about the development of the trend. Among the variety applications, Folksonomy shows much potential in library information services. This paper first introduces the respective definition and development of Web 2.0 and Folksonomy. Next, the study further discusses their implications in areas of information organization and information retrieval. Finally, future roles of librarianship in accordance with the new trend are also explored.