Smart technologies should make cities, governments, and societies not only more efficient and sustainable but also more livable. First, the conceptual framework of smart cities and societies is reviewed. At first glance, it seems promising to implement AI-based systems to address the latent needs of citizens. However, which conception of justice this presupposes has not been sufficiently scrutinized. Second, different conceptions of justice are shortly discussed. It is argued that conceptions of justice are context-dependent, i.e., while in one context, one conception of justice could be considered ethically acceptable, in another context, it might be considered unacceptable. Third, the limits and ethical implications of operationalizing justice via algorithms are analyzed.