This looks equally bad on the EU, that they lacked the foresight to see that phone numbers in the WhatsApp database could be matched with phone numbers in the Facebook database.
If you read the case decision, specifically paragraphs 137 - 140 it becomes even more ridiculous: http://ec.europa.eu/competition/mergers/cases/decisions/m721... This quote sticks out as a bit of an exaggeration regarding the difficulty of this operation: "Notably, integration of WhatsApp's and Facebook's networks would require matching WhatsApp users' profiles with their profiles on Facebook (or vice versa). This wo…
For some time now, facebook has been requiring a phone number to register. In some cases, they don't ask for one until you try to add people, or something alike. If you use Facebook Messenger (with no facebook account), you can sign up using ONLY you phone number.
This was just a plain lie.