Beginning with iOS 10, Apple will also employ a relatively new technique called Differential Privacy, which basically crowd-sources information in a way that doesn’t identify individuals at all.
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Exactly how it should be done — as long as their are no logical leakages i.e., relationship types semantics can actually reveal otherwise hidden identity. For instance, identifiers such as Email Addresses, Home Page URLs, Profile Page URLs etc.. are ultimately mechanisms for revealing personal identities.