"Search engines are increasingly important to people in their navigation of information spaces, but users are generally uncomfortable with the idea of their search histories being used to target information to them," said Kristen Purcell, author of the report "Search Engine Use 2012."

"A clear majority of searchers say that they feel that search engines keeping track of search history is an invasion of privacy, and they also worry about their search results being limited to what's deemed relevant to them," Purcell said in a news release.

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