“But what else can these searches reveal? For one thing, doppelgänger searches have been used by many of the biggest internet companies to dramatically improve their offerings and user experience.”
[Everybody lies, Seth Stephens-Davidowitz]
There is an urban legend about a doppelganger, a non-biologically related look-alike or double of a living person; If you meet a doppelganger, you will die. We know this is fictional but nobody wants to meet her/his doppelganger.
In data science, however, meeting a doppelganger is helpful to understand and predict. In Big Data, we have assumed that similar input data, like a doppelganger, has similar output. Hence, if we can find doppelgangers of the target, we can predict its output effectively (e.g. averaging output of doppelgangers like a k-nearest neighbor or kNN). For example, Amazon and Netflix figure out what you might like from your doppelgangers in their database.
Everybody makes DATA 