Smart City infrastructures connect people with their devices through wireless communications networks while they offer sensor-based information about the city’s status and needs. Connecting people carrying mobile devices equipped with sensors through such an infrastructure leads to the “collective intelligence” or “crowdsourcing” paradigm. This paradigm has been deployed in numerous contexts such as performing large-scale experiments (e.g. monitoring the pollution levels or analyzing mobility patterns of people to derive useful information about rush hours in cities) or gathering and sharing user collected experiences in efforts to increase privacy awareness and personal information protection levels. This chapter focuses on employing this paradigm in the mMarketing/mCommerce domain and discuss how crowdsourcing can create new opportunities for commercial activities as well as expansion of existing ones.