1. A method comprising: collecting activity data from a plurality of Web sources using a plurality of collection devices; based the activity data, forming a social graph having a first node and a plurality of first-degree nodes connected to the first node, wherein each first-degree node is connected to a plurality of second-degree nodes; determining edges between first-degree and second-degree nodes comprise a first category type; determining no edges exist between the first node and the first-degree nodes of the first category type; and based on the edges of the first category type between first-degree and second-degree nodes, using at least one processor, making an inference that the first node has an interest associated with the first category type.