When Apple said that iMessage uses end-to-end encryption, everyone started complaining that it's not real end-to-end since we have to trust Apple for key exchange.

Now we have the same thing with What's App: we have to trust them with the key exchange. It's marginally better, since they have an optional way to enable notifications after a key was changed.

I applaud the Guardian to run with the story. Whether to call it a back door / flaw / trade-off is just quarreling over semantics, when the important part is that you need to trust a central service.

If you want to be sure that noone can intercept your messages, use PGP or S/MIME, (preferably encrypting your message on an air-gapped computer)

Saying that we shouldn't worry about state-level actors is a bit naive after PRISM was revealed.

If you are doing something that someone in power might dislike, you should not rely on Whats App.