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The most popular way to defeat email based user privacy services (as provided by Apple, Firefox, etc.) is to require a phone number for "verification" or "security" purposes.

In addition to being harder to acquire in bulk, phone numbers serve as a convenient non-anonymous and universal user identification key that can be easily matched by data brokers and shared to track customers across multiple businesses.

Facebook pioneered this approach by adopting SMS-based 2FA as a means of acquiring phone numbers to match users with purchases at partner businesses.

Phone numbers also enable businesses to send unsolicited text messages and robocalls.