This article develops a social epistemological analysis of Web-based search engines, addressing the following questions. First, what epistemic functions do search engines perform? Second, what dimensions of assessment are appropriate for the epistemic evaluation of search engines? Third, how well do current search engines perform on these? The article explains why they fulfil the role of a surrogate expert, and proposes three ways of assessing their utility as an epistemic tool—timeliness, authority prioritisation, and objectivity. “Personalisation” is a current trend in Internet-delivered services, and consists in tailoring online content to the interests of the individual user. It is argued here that personalisation threatens the objectivity of search results. Objectivity is a public good; so there is a prima facie case for government regulation of search engines.