So let me share some insight from handling encryption issues with people over a decade now. If the software is truly non-backdoor'd as they will claim, then how will the various cell providers handle the lost/forgot password irrate customer? You think that isn't going to happen in aggregate? Or what about the angry significant other that changes the password and then says "~ Snipped as per TOS ~ you" after handing the phone back and walking out the door? All issues and so little time in a busy retail store. LOL!!
They won't. The user failed to follow instructions that, no doubt stated in large capital letters, "DO NOT LOSE YOUR PASSWORD". Use the opportunity to exercise better judgement in selecting a significant other and follow the remaining all-caps instructions, "DO NOT GIVE ANYONE YOUR PASSWORD!"
It's rather misleading calling it FDE though isn't it, as it only encrypts the data partition, not the system partition where the OS and apps are stored, so those are left vulnerable to being tampered with, malware installed, etc?
