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.
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. 5. The method of claim 4 , wherein the calculating of the document value comprises a weighted combination of the ratings parameter and the readership volume parameter, the ratings parameter being given a greater weight than the readership volume parameter.