Increasingly thinking it’s time to leave Facebook. This psychiatrist’s experience is just creepy.

All these patients likely have Lisa’s number in their phones, so an algorithm analyzing this network of phone contacts might reasonably assume all these people are connected. A phone number alone can be quite a revealing bit of information, which is why it’s so significant that WhatsApp is about to share its one billion users’ phone numbers with Facebook, where they too could be used to make friend recommendations (unless you opt out).