This article analyzes the issue of degradation of data accuracy in large-scale longitudinal data sets. Recent research points to a number of issues with large-scale data, including problems of reliability, accuracy and quality over time. Simultaneously, large-scale data is increasingly being utilized in the social sciences. As scholars work to produce theoretically grounded research utilized "small-scale" methods, it is important for researchers to better understand the critical issues associated with the analysis of large-scale data. In order to illustrate the issues associated with this type of research, a case study analysis of archival Internet data is presented focusing on the issues of degradation of data accuracy over time. Suggestions for future studies are given.