Comment by ninkendo

My 2¢, as someone who tried using WhatsApp once and ran away screaming:

WhatsApp requires you to give it access to all your contacts (your entire address book) in order to use it at all. This information is uploaded straight to Facebook’s servers where they’ll inevitably use it to place your WhatsApp account in a social graph so they know who you are based on your contacts. I found this to be unacceptable so I uninstalled it.