Testing the validity of indicator systems is a task almost always left to the scientific community, in standard practice and in keeping with the quest for objectivity prevalent in politics and in society as a whole. This paper calls for a reinvigorated agenda within indicators research to question this practice and develop alternative methodologies to test the validity, legitimacy and impacts of indicator systems. The assumptions of objectivity are not realistic in contemporary policy contexts. As a result, the scientific community is not the only community with a stake in assessing an indicator system; it is perhaps not even the most important one. Four other community types with distinct interests in the design, use and impacts of indicator systems are identified. First is the community of elected officials, whose positions of power make their perspective important and unique; second is the community of engaged publics, whose stake is made clear by the principles of participatory and deliberative democracy; third are communities of cultural difference; and fourth are professional communities. The unique relationship each of these communities has with indicator systems, and thus the tests and challenges offered by each to the practice of indicators, is discussed through a case study of a public participation process for the development of a new set of regional sustainability indicators in Vancouver, Canada. The evidence suggests new research questions for scholars in policy and indicators studies who seek to better understand paths and barriers to implementation and impact in indicators practice, as well as lessons for other local indicators practices.