1. A method comprising: accessing one or more memories that store document information about documents in a knowledge base, the document information identifying relationships between the documents and contributors to the knowledge base, and personal network information with respect to personal networks of respective contributors to the knowledge base, each personal network defining personal connections between respective contributors forming part of the personal network, wherein each personal network is structured such that nodes of the network are provided by the respective contributors, each personal connection comprises a connection defined directly between two of the nodes of the personal network; and in an automated operation using one or more processors, calculating respective ranking values for two or more of the contributors, the calculating of the respective ranking values comprising, for each of the two or more contributors: calculating a document factor calculated as a quantified value based on one or more properties of the document information for the corresponding contributor, calculating a personal network factor calculated as a quantified value based on one or more properties of the personal network information of the corresponding contributor, and calculating the ranking actor based at least in part on the document factor and based at least in part on the personal network factor.