When will we start talking about metadata when talking about privacy?
Just read the "privacy" statement from WhatsApp: They basically say that they won't listen to your conversation, but they capture your IP, your device information (including your battery charge, for some reason) and who you're talking to and they may share it with their other providers (one of those being Facebook itself).
Now, sure, they can't take what I'm talking to my wife, but they can surely see that her IP is not the same as mine for awhile and that there is a rising conversation from me with a lawyer.
And it is not hard to figure out what's going on...
PS: That's just an example. I'm not getting divorced -- I'm not even married, for that matter -- but you get the gist, right?
Meanwhile, we are just going Hooray for anything that says "end-to-end encryption" and whatnot and caring about this kind of stuff.