The current dominant theory concerning the diffusion of innovation (DOI) was proposed by Rogers (1995). Its ontological basis is Social Constructivism (SC). This paper suggests that SC leads to explanations that are not valid in some industry environments. This paper further suggests that these limitations can be overcome by adopting a Critical Realist ontology (CR). Social constructivism does not allow for the possibility that external forces can determine how a business operates but lead one to believe that that management, independent of these external forces, determines the structure and mode of operation of its business. Research was conducted into the uptake of the IS-enabled listing, sales and clearance systems and the resultant structural changes in the stockbroking sector of the finance industry. It was found that, in this industry-sector, government and professional and regulatory bodies have had an overwhelming influence on the form of, extent and the technological requirements that stockbrokers needed to adopt should they wish to operate in the sector. It was also observed that these regulatory bodies affected the extent to which the firms could use the Internet to transform the business and the procedures firms could use. In addition the compulsory use of the trading systems imposed on the then present and prospective brokers acted as a barrier to entry thus maintaining a balance based on the predefined criteria designed and implemented by the sector’s regulatory bodies. The paper disputes the condition, stated by Rogers(1983), that technology adoption can be examined independently of the role of these important external impositions. Hence a critical realist lens was employed as an underlying philosophy to help explain the observed technology adoptions. The benefits of such a philosophical grounding are highlighted.