As the Facebook–Cambridge Analytica data scandal showed, the social network algorithms can be used to send political messages according to your psychological profile. (Political messages shown to you, can be different from political messages shown to your neighbor).

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Donald Trump's 2016 presidential campaign used the harvested data to build psychographic profiles, determining users' personality traits based on their Facebook activity. The campaign team used this information as a micro-targeting technique, displaying customized messages about Trump to different US voters on various digital platforms. Ads were segmented into different categories, mainly based on whether individuals were Trump supporters or potential swing votes. As described by Cambridge Analytica's CEO, the key was to identify those who might be enticed to vote for their client or be discouraged to vote for their opponent. Supporters of Trump received triumphant visuals of him, as well as information regarding polling stations. Swing voters were instead often shown images of Trump's more notable supporters and negative graphics or ideas about his opponent, Hillary Clinton. For example, the collected data was specifically used by "Make America Number 1 Super PAC" to attack Clinton through constructed advertisements that accused Clinton of corruption as a way of propping up Trump as a better candidate for the presidency

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https://en.wikipedia.org/wiki/Facebook%E2%80%93Cambridge_Ana...