Fuchs 2008, Internet and Society: Social Theory in the Information Age -- says it is central reciprocity emerges as obligation and social pressure -- Dourish in From Social Butterfly to Engaged Citizen 2011 Lampel 2007 J of Computer_mediated communication, 12: 434 Pearson 2007 in First Monday 12(5) online hounral Benkler calls it sharing but also says it is central, Wealth of Networks, 2006