To further the analogy, Alice and Bob decide on potentially emailing Anna instead but Zuckerberg is such a megalomaniac that he's overriden everybody's email addresses https://news.ycombinator.com/item?id=4151433
("But that's on Facebook, which Anna doesn't have" - true, but apparently syncing contacts with Facebook - something FB presumably often does automatically - will wipe out email addresses of your contacts)
("But that's on Facebook, which Anna doesn't have" - true, but apparently syncing contacts with Facebook - something FB presumably often does automatically - will wipe out email addresses of your contacts)