To the Editor: In their Research Letter study, Dr Keelan and colleagues1 evaluated YouTube as a source of information on immunization. Previous reports have indicated an increasing use and inconsistency in the quality of online sources of information about vaccination.2-4 However, we are concerned that the application of a formal appraisal to a freeware Web site that is unregulated, uncensored, and designed more for entertainment than the dissemination of evidence-based medical advice may lend false gravitas to an unstructured, unvalidated online rating system as well as medical credence to a conduit of popular culture.