But personalization can also work against you. If for instance Google wants to favour one political candidate over another they could "personalize" your search results by boosting positive sentiment articles and filter out those with negative sentiment towards that candidate. And since Google search is still viewed as fairly objective it could have massive impact, and since it's personalized it's very hard to detect.

https://www.wired.com/2015/08/googles-search-algorithm-steal...

http://www.bbc.co.uk/news/election-2017-39938599