Tails

Tails by default is Amnesic. Adding a persistent volume makes Tails less Amnesic, thus creating a potential risk for a person who is forced to decrypt their USB.

Having a feature that allows for the already existing passphrase #1 to be used to unlock the actual persistent volume, while adding the option to also set a passphrase #2 for a decoy persistent volume, would allow someone to decrypt one of their Tails persistent volume, keeping the other one hidden from sight, and show dummy/decoy information. Such as another email address for Thunderbird, or other servers and stored credentials for the SSH client.