Preliminary research at MSU by Ellison, Steinfield and Lampe  (http://jcmc.indiana.edu/vol12/issue4/ellison.html) suggests Facebook works in Granovetter’s realm of weak ties.  This is good news for social capital (though the concept itself undergoing major reconceptualization).  The question is whether this can amount to something other than mere capital accumulation by the already-well-resourced.