A method and system for associating a physically identifiable feature of a person with the unique identifier of a mobile device carried by the person as detected across repeat visits to a physical location or multiple locations. Specifically, associating the face of a repeat visitor with a unique identifier of a mobile device, such as the device's MAC address, by means of a repeat visit analysis without any explicit or voluntary participation of the person, for example, in a form of providing their information by participation in a survey. For each detection of a particular MAC address associated with a mobile device at a particular physical location, a set of candidate faces can be captured at that physical location. Revisiting faces can be identified and grouped together, and a probability that each group of faces is associated with a particular MAC address can then be calculated. After satisfying several constraints, a maximum probability can be determined, resulting in a match of a particular face to a particular MAC address.