I just saw the below and am now on the fence again about deleting WhatsApp (despite its past glowing EFF review and even recommendation):
Tl;dw: WhatsApp is integrating users' information with Facebook, suddenly connecting complete strangers through "recommendations" both can see, like the patients of the psychiatrist in this story. It's unsure what these recommendations are based on but suspicions point to geolocation and membership of the same address book. Implications for more severe threats (eg: stalkers, journalists' sources) arise immediately. From a deeper analysis: "Thanks to tracking the location of users’ smartphones, the social network may suggest you friend people you’ve shared a GPS data point with, meaning your friend suggestions could include someone whose face you know, but whose name you didn’t until Facebook offered it up to you." Chilling.
Thoughts? Is WhatsApp secure?