There is currently much international interest in principles and processes for determining which services should qualify for health insurance packages. However, there has yet been little analysis of the implications of actual deinsurance decisions made by such priority-setting exercises. This paper reports experience from the case of in vitro fertilization (IVF) deinsurance in Ontario, Canada. The analysis addresses some of the more social aspects of financial incentives by characterizing funding structures as means of communicating complex policy objectives, rather than mechanistic reward-penalty systems. Deinsuring IVF was intended to support several policy goals, including: controlling public expenditures, restricting public coverage to 'medically necessary' services, applying evidence of effectiveness as a criterion for medical necessity and implementing part of a policy program to control new reproductive technologies. It may seem a modest step to remove one dubious service from public insurance coverage. Nevertheless, as interpreted by stakeholders, deinsurance of IVF may inadvertently promote the opposite of what policy makers intended. This case suggests that priority-setting decisions based on incomplete information, inconsistently applied principles and too little attention to health system dynamics (perhaps the norm in 'real-world' priority-setting) can have the perverse effect of undermining progress toward health reform goals of improved health, reduced expenditures and more rigorously evaluated services. The case of IVF in Ontario offers several lessons for other jurisdictions engaged in priority-setting and service deinsurance: (1) individual services interact with the rest of the system and cannot be removed without systemic effects, (2) inconsistent use of coverage principles can undermine legitimacy of both priority-setting principles and processes and (3) 'evidence-based' decisions can founder on differing stakeholder ideas about appropriate evidence and on the inconsistent message given by commercializing ineffective or unproven care.