Smart sensors and actuators, embedding learning and reasoning features and associated to everyday objects and locations, will soon densely popu- late our everyday environments. Being capable of understanding, reasoning, and reporting about what is happening (for sensors) and about what they can make possibly happen (for actuators), these “speaking objects” will thus be assimilable to autonomous situated agents. Accordingly, populations of speaking objects will define dense and massive multiagent systems, devoted to monitor and control our environments, let them be homes, industries or, in the large-scale, whole cities. In this context, the necessary coordination among speaking objects will be likely to become associated with the capability of argumenting about situations and about the current state of the affairs, triggering and directing proper distributed conver- sations, and eventually collectively reach future desirable state of the affairs. In this article, we detail the speaking object vision, overview the key enabling tech- nologies, and analyze the key challenges for engineering large-scale collectives of speaking objects and their conversations.