Considerable attention has been paid in recent years to the fundamental changes in the global tourism system related to the emergence of information technologies (IT), and, specifically, the rise of social media. Opportunities to search travel-related information, to reserve and book, evaluate and judge; to receive travel advice and to communicate one's mobility patterns have all profoundly changed the practices of performing tourism, with concomitant repercussions for the management and marketing of businesses and destinations. This paper provides a discussion of the implications of these changes for the sustainability of the global tourism system. Based on an exploratory research design, key changes in the tourism system are identified and discussed with regard to their environmental, socio-cultural and psychological, as well as economic significance. The paper concludes that IT affects the tourism system in numerous and complex ways, with mixed outcomes for sustainability: while most changes would currently appear to be ambivalent – and some outright negative – there is considerable potential for IT to support more sustainable tourism. Yet, this would require considerable changes in the tourism system on global, national and individual business' levels, and require tourism academics to probe many new issues.