Several studies have addressed the issue of what makes information on the World Wide Web credible. Understanding how we select reliable sources of information and how we estimate their credibility has been drawing an increasing interest in the literature on the Web. In this paper I argue that the study of information search behavior can provide social and cognitive scientists with an extraordinary insight into the processes mediating knowledge acquisition by epistemic deference. I review some of the major methodological proposals to study how users judge the reliability of a source of information on the World Wide Web and I propose an alternative framework inspired by the idea that–as cognitively evolved organisms–we adopt strategies that are as effortless as possible. I argue in particular that Web users engaging in information search are likely to develop simple heuristics to select in a cognitively efficient way trustworthy sources of information and I discuss the consequences of this hypothesis and related research directions.