3. The method of claim 2 , wherein the calculating of the document factor for a particular contributor comprises calculating respective document values for multiple documents to which the particular contributor has contributed.
3. The method of claim 2 , wherein the calculating of the document factor for a particular contributor comprises calculating respective document values for multiple documents to which the particular contributor has contributed. 4. The method of claim 3 , wherein the calculating of the document value for a particular document is based at least in part on: a readership volume parameter representative of the number of contributors who have read the particular document; and a ratings parameter derived from ratings of the particular document by respective contributors.