Teaching old dogs new tricks is difficult, but lessons learned from such efforts can be invaluable. Warfarin is an old drug, difficult to administer and a leading cause of drug-related mortality and hospitalizations. New genetic tests for optimizing warfarin therapy have not been adopted. The debate over precise clinical utility and cost-effectiveness of these tests misses more important points of building a better, cheaper, and more efficient infrastructure to measure the true real-world impact of personalized medicine. However, this same debate about how, when, and where such testing is appropriate has been invaluable to the field of personalized medicine: progress beyond science, in policy, regulations, and logistics can be highlighted along the path to safer and more efficacious warfarin therapy.