I'm glad you do but I suspect most people don't. It takes a mental leap to realise that other people can now (unknowingly) do things that expose your information to parties you're trying to avoid sharing with. Even writing it now I feel like it's obvious but people I speak to really don't understand how things work.

Couldn't agree more. I was off Viber, or WhatsApp for about 3 months. Had closed the accounts after installing and I had moved to TextSecure and Telegram. I was successful in convincing some friends to join Telegram (they were still on Viber/Whatsapp) but I had 0 friends on TextSecure. Finally Telegram friends uninstalled it. As I was missing a lot of messages, fun, and info about common friends I came back to WhatsApp and Viber and that made me sad. I tried to explain what Facebook buying WhatsApp meant, it didn't work. They don't give a damn and I talking about intelligent technocrats who passed from the best tech schools in the country and are in the best s/w jobs. Privacy is a cultural thing.