1. A computer-readable medium storing computer-executable instructions for causing a computer-controlled apparatus to implement a tag-mediated review system for electronic content, comprising the step of: obtaining on-line access to an infrastructure of electronic content including a plurality of electronic source documents, wherein each electronic source document comprises source content supplied by an associated content producer and a plurality of tags identifying subject matter addressed by the source content; receiving a plurality of reviews concerning the source documents, each review expressing quality assessment information for a source document by an associated reviewer and one or more tags identifying subject matter addressed by the review; computing a tag-mediated content quality score for each source document based at least in part on the reviews, wherein each tag-mediated content quality score includes tag scores for one or more tags in the associated source document; compiling a content quality information database storing the tag-mediated content quality scores in association with the associated tags and identifiers of the associated source documents; receiving a document retrieval request; retrieving information pertaining to one or more source documents responsive to the document retrieval request and the tag-mediated content quality scores associated with the responsive source documents; and displaying information identifying the responsive source documents and the associated tag-mediated content quality scores or ranking the responsive source documents in a priority order based directly or indirectly on the tag-mediated content quality scores and displaying indicators for the responsive documents in the priority order.