The advancement of information technology together with the force of globalization has contributed to the growth of e-service industries. In this article, we propose an intelligent Delphi-based group decision making mechanism within an implemented system (iDecision). We also utilize case-based reasoning (CBR) as the major inference approach in the process. The growing practice of online collective wisdom has indicated the potential of agent-based systems via the Internet. This article provides a further contribution to the existing practices with the suggestion of synthesizing the process of Delphi method into the collective intelligence (based on the social network).