Like it or not librarians and doctors, "Millions find health tips a Web click away." According to a study by the Pew Internet & American Life Project, 113 million adult Web users in the U.S. who have gone online for medical advice and research. About 10 million Americans search the Internet each day for health information, making it as common an activity as online bill paying, reading blogs, and looking up phone and address information. "Just 15% of health seekers say they 'always' check the source and date of the health information they find online, while another 10% say they do so 'most of the time.' Fully three-quarters of health seekers say they check the source and date 'only sometimes,' 'hardly ever,' or 'never,' which translates to about 85 million Americans gathering health advice online without consistently examining the quality indicators of the information they find."

Which brings me to the article "Want to See the Sites? Better Find a Better Guide: Do Popular Search Engines Return Librarian-Recommended Sites? " in Internet Reference Services Quarterly 2006 v. 11 (3) by Tyler, Childers, McNeil, and Dostal.
Abstract:
This paper presents the results of a study of the utility of several popular search engines and of two newer search engines with respect to librarian-selected lists of Web resources and internet searching behaviors. This study addresses whether said resources are returned where internet searchers could reasonably be expected to find them and whether the search engines employed serve as acceptable substitutes for the expert advice of librarians. Search engines included in the study were Google, MSN.com, Yahoo, Lycos, AskJeeves, Icerocket, and Acoona. Searches for the study were based on the topics/titles of the “Internet Resources” columns from College and Research Libraries News for 2004. Finally, the paper addresses methodological concerns and proposes possible directions for further research.

Reading both articles librarians and researchers are able to get a better understanding of searchers methodologies and the web tools (search engines) they choose.