Hola Francisco;
Nope, its not. But it would not hurt for you to copy the activation-key in case something happens to the flash and you need to re-enter it.
You can find the activation key using the "show version" command.
The reason why it is on clear text is due to the fact that it is tied to the serial number, so if you try the same activation code on another box, it would not work.
Cheers;
Mike.
Mike