True but surely it's only as secure as your device as the App starts up without the need for any additional login details? If you haven't got security activated someone can still pickup your device and read your chat history and send something malicious if they so wanted (as it is in WhatsApp, Google, FBM, Etc).
Security like this is only really attractive to businesses rather than your average 20yr old sending pictures of their tits to blokes.
I'm glad you mentioned PINS to as I always found them annoying even as a RIM-Boy. Quick codes are equally as bad to as you physically need to exchange details like its 1991 all over again where as WhatsApp just scans your devices contacts App and automatically adds peoples numbers from your phone book that also use the service... far more simple than saying to someone "What's you PIN" and then everyone looking at you like you've got AIDS.
Mick
PS: I honestly used to love RIM/BB/BBM but they should have done this nearly two years ago now rather than clinging to it like some kind of avantgarde premium service.