The Southern Leaf Blight (SLB) epidemic of 1970 is considered a key historical example of the vulnerability that can occur from narrow crop diversity. Corn yields were decimated by 50% in some states, and approximately 15% nationwide; losses would have been much worse if it were not for dry weather in the north and west. A National Academy of Sciences inquiry posed fundamental questions: What happened? Why was it not foreseen? Where did the technology go awry? Key lessons were: "Genetic uniformity is the basis of vulnerability to epidemics", "uniformity derives from powerful economic and legislative forces", and "the nation should provide facilities for continuously maintaining gene pools". Over 35 years later much has changed including the technologies, use of intellectual property protection, sources of germplasm, and business structure of the U.S. corn industry. All of these factors impact genetic diversity and the resultant balance between genetic gain and genetic vulnerability. The inevitable outcome of effective breeding programs will be a continued narrowing of genetic diversity, unless mechanisms are deployed to oppose the effect of anticipated narrowing. Today's technologies provide a genotypic view and can allow more effective use and monitoring of genetic diversity as it directly relates to trait variation (diseases, insects, biotic and abiotic factors) including to monitor for situations of potential vulnerabilities in the germplasm base upon which the human population depends for food, feed and industrial purposes. These tools can also be utilized for intellectual property protection to encourage further investment into the improved performance of varieties including through the use of more exotic germplasm. I will conclude with a summary of what has been achieved and what yet remains to be achieved.