Recently, several studies suggested that the amount of online search queries can be used as an indicator of the public agenda. Based on former research by the authors, this article discusses the role of public uncertainty as another factor influencing search queries. Therefore, the influence of media coverage on Wikipedia searches concerning two issues is compared: one issue with uncertainty (the Enterohaemorrhagic Escherichia coli [EHEC] epidemic), and one without uncertainty (unemployment). Analyses show much stronger correlations in the case of EHEC, which suggests that online search behavior may especially be used as an indicator of the public agenda in case public uncertainty exists.