The movement from the physical to the digital library offers both dangers and opportunities. Alongside the greater quantity of online material goes the problem of quality assurance: how can be the information searcher be sure of the status of a document. We suggest that this be addressed by supporting recommendations and that the key feature that links these recommendations together is that of usage. The main use of usage data within information science is currently that of a research tool in the form of transaction log analysis. In a digital library this data, together with other evaluations and recommendations, can enrich the existing information structure. Several approaches to the integration of usage data are described together with their respective costs and benefits. The social implications of these possibilities are discussed with particular reference to the privacy of usage data.