Jamie Lawrence works on very promising topic:

What if every Bluetooth device was constantly on, constantly broadcasting "information" and constantly receiving it? What information would people share, how will users manage this information flow, how will they experience it, what are the technical problems and opportunities, what are the social problems this technology might solve and what are the social issues it will create? Using the temporal and spatial patterns prevalent in urban society, this local broadcasting may be an effective, decentralised, alternative to location tagging (as in Urban Tapestries). Or, it might not.