Participatory Sensing Systems enabled through a billion smartphones

What can you do with a billion smartphones ? Participatory sensing seems an obvious choice or at least it was back in 2008-2009. From the Urban Sensing/CENS website:

Participatory sensing. urban sensing is about people like you—equipped with today’s mobile + web technology—systematically observing, studying, reflecting on, and sharing your unique world. through discovery and connected participation, you can see the world anew. you can tell your local story. you can make change.   

Another related project using compressive sensing is Ear Phone. Similar participatory projects also include

• a participatory noise mapping projects in Brussels and
• a participatory  thermal effects in the atmosphere monitoring of the Swiss Alps ( Project Ikarus: Large-Scale Participatory Sensing at High Altitudes)
• GreenGPS uses participatory sensing data to map fuel consumption on city streets, allowing drivers to find the most fuel efficient routes for their vehicles between arbitrary end-points. 

Additional participatory projects can be found at http://participatorysensing.org/

In 2011, it seems that the momentum has been lost for implementing these systems. The issue of privacy has so far not been resolved as a whole (see the iPhone/Android Geolocation headlines of this past year) with the general population.