[throwaway78981]

This isn't true. The phonebook we had had only Name, Phone number and very broad location. Also those days, phone number was just that - a phone number. Nowadays it's a unique identifier for lots and lots of things including government stuff. Some government stuff even uses it for authentication/authorization.

Also I guess user ID means it gives access to their fb profile page I guess? From there one can scrape pics etc (public ones).