Open Whisper Systems partners with WhatsApp to provide end-to-end encryption

This is really huge, WhatsApp has incredible market penetration in lots of countries. Almost every smartphone user in Brazil uses WhatsApp, and businesses of all kinds (eg. radio stations, pizza deliveries and drug stores) have a WhatsApp number for connecting with their customers.

I also have TextSecure and Telegram installed but almost none of my friends do, and telling non-techie people to install another IM app because it's more secure then WhatsApp is futile.

I'm curious to why WhatsApp is not advertising this collaboration.

Also, I wonder if there's some visual indication that end-to-end encryption is enabled for a given contact/conversation like the padlock icon in TextSecure (which can fallback to SMS).