Nicola Guarino has coined the phrase ontology driven information systems. This phrase appears to offer ontology based help and guidance for information systems development. In this paper we try to understand better whether, why and where ontology affects information systems. We briefly discuss what kind of help we would appreciate and identify domains of knowledge in information systems development that according to our point of view could benefit from such help. We briefly discuss the following five domains: universes of discourse, information systems resources, information space use, customers, and human inference making.