WhatsApp for iOS moves to yearly subscription model5
Of course, as with the Android version of the app, downloading it will get you a year free before you have to start paying the annual subscription. So, what this really means is that WhatsApp is now free for iOS users, and you get a one-year trial. Although, calling it a trial probably isn't quite right, since after a year, you'll have either uninstalled the app or are completely hooked.
Given that WhatsApp recently announced 250 million users, it seems quite a few are getting hooked.