What do you think of big data used in campaigns?

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I read an article: The Data that Turned the World Upside Down 
Basically it talked about big data using FB to run Brexit and Trump campaign. It is fascinating. 
Even further there is a webpage called applymagicsauce.com which is referenced in the article. It can show you your personality type, political offiliations, sexual orientation, and a lot more based on your Facebook movements. What do you all think of big data? Do you think that is how campaigns are won? Do you think it is ethical? 

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