If/When Native Email comes to the PlayBook Wifi/4g/3g models, I hope this will be a forced addition, should be inline with their security. Maybe an implementation similar to the Android Swipe for a passcode.
PB OS2 fixes this for those of us with corporate email and BES servers. Blackberry Balance allows administrators to install BBBalance and lock email away with a password from the rest of the device. Fantastic addition however it still gives us grief with non BES areas that we'd like to secure. For example, I would still like to secure my personal email from my kids playing Angry Birds on my Playbook. We still have a gap here in between corporate and personal.
Ask:Please configure application level locking control on the personal side of Balance so I don't have to worry that my 4 year old is arbitrarily replying giberish on my personal email/calendar application.