Embodiments of computer-implemented methods, systems, computing devices, and computer-readable media are described herein for opportunistically transitioning service flows of mobile devices between being direct and indirect. In various embodiments, a proximity between first and second mobile devices that are in wireless communication with each other may be monitored. In various embodiments, a selective transition of a service flow between the first and second mobile devices from being indirect through the radio network access node using a first radio access technology (“RAT”) to being direct using a second RAT may be facilitated, e.g., responsive to a determination that a first criterion has been met. In various embodiments, a selective transition of the service flow from being direct using the second RAT to being indirect using the first RAT may be facilitated, e.g., responsive to a determination that a second criterion has been met.