Social Networks represent ones of the most mature expressionof Web 2.0 advent. If from one side, social networkingsites provide us the opportunity to browse new digitalworlds, make friends, share moments and resources withthe rest of the internet community, from another side theyrepresent a sophisticated tool for measuring properties of agroup of people, allowing for the extraction of up-to-date,valuable and full of context information. In this paper weinvestigate how the above Social Sensing can be integratedin pervasive services and infrastructures. In particular, weframe the possible approach that can be undertake to pursuesuch integration, and survey the leading proposals inliterature. From the limitations of actual approaches andimplementations come a general discussion on open issuesand challenges that researchers have to overcome to makesocial sensing a general-purpose tool for forthcoming pervasiveapplications.