E-mail spam has been the focus of a wide variety of measurement studies, at least in part due to the plethora of spam data sources available to the research community. However, there has been little attention paid to the suitability of such data sources for the kinds of analyses they are used for. In spite of the broad range of data available, most studies use a single "spam feed" and there has been little examination of how such feeds may differ in content. In this paper we provide this characterization by comparing the contents of ten distinct contemporaneous feeds of spam-advertised domain names. We document significant variations based on how such feeds are collected and show how these variations can produce differences in findings as a result.