I particularly like that social capital originally meant the set of capital equipment you could borrow from your acquaintances; doesn’t seem to mean that anymore since information (a public/club good) is typically what people now think of as what travels thru the social network.

From http://www.bowlingalone.com/socialcapital.php3 :

The central premise of social capital is that social networks have value. Social capital refers to the collective value of all “social networks” [who people know] and the inclinations that arise from these networks to do things for each other ["norms of reciprocity"].