According to Toshiba, the new wipe technology on their self-encrypting hard drives will destroy any data in them when you remove the device or power it off completely. Sounds a bit nuts, but it makes sense.
Instead of overwriting the data, which takes hours, or using a physical method that requires time and effort - the new drives will automatically invalidate the data in just a few seconds by erasing its HDD security key when the power is completely off. This means that any confidential documents stored in the hard drive - like an office printer - will be safe in case someone extracts the HD or the device is stolen and disconnected from the power outlet. [Toshiba]