1. A computer implemented method comprising: obtaining wireless contexts of a plurality of mobile devices of a corresponding plurality of users, wherein for each mobile device of at least some of the plurality of mobile devices, the wireless context of the mobile device comprises a wireless Personal Area Network (PAN) context of the mobile device comprising information identifying one or more PAN-enabled devices detected by the mobile device and a quality metric for each of the one or more PAN-enabled devices detected by the mobile device; and forming one or more crowds of users based on the wireless contexts of the plurality of mobile devices.