As mobile Internet usage continues to grow, the phenomenon of accessing online communities through mobile devices draws researchers’ attention. Statistics show that close to 60 percent of all mobile Internet traffic worldwide is related to the use of mobile social networks. In this chapter, the mobile social Web is defined, categories of mobile communities explained, and success factors and drawbacks discussed from the technical, social, and economic perspectives. Challenges, including low transmission rates, changes in usage patterns, search for new revenue sources, as well as the need for development of original mobile Web content and applications are addressed. The technical requirements for the mobile use of online communities are identified. The chapter closes with a summary of potential economic and social prospects of the emerging mobile social Web.