While human-free wireless sensor networks have been primarily the purview of academia, human-centric sensing has
attracted top industry players from the very outset, and in fact the extraordinary uptake of smartphones and their nearly
universal appeal have caused the research community to shift its focus toward the human-centric paradigm in recent years.
In the golden years of human-free sensor networking (2003 through 2009), the lack of mainstream appeal of mote-like
devices was generally dismissed as inevitable, and the absence of solid industrial interest was blamed on the lack of a killer
application. Nevertheless, it is unlikely for any technology to ever become truly pervasive if it lacks mass appeal; in our view,
human-free sensor networks may have overestimated their potential for pervasiveness in the pre-smartphone world