Pew Internet | US | Search engine use 2012 (page links to PDF)
From the summary of findings:
“65% say… It’s a BAD thing if a search engine collected information about [their] searches and then used it to rank [their] future search results, because it may limit the information [they] get online and what search results [they] see […] 73% say they would… NOT BE OKAY with a search engine keeping track of [their] searches and using that information to personalize [their] future search results because [they] feel it is an invasion of privacy […] 68% say… [they’re] NOT OKAY with targeted advertising because [they] don’t like having [their] online behavior tracked and analyzed”
(Source: epic.org)