Perhaps I was being a tad flippant in my post on WhatsUp, not naive as quoted previous.
You can have all the security possible to protect yourself, but at the end of the day, there's always back doors, as you have said, and if the security services want to go places, I'm damn sure they will...
I'm guessing most WhatsApp users, like myself, just use the app, because it's free for most to send images, videos, and phone and video calls.
If you have nothing to hide, then there's no problem.
The encryption thingy is just gimmicky really. IMO
Unless you're all budding secret agents!