As others have noted, it is partially because Crashplan is a Java based app. Partially, it is also because Crashplan runs as System, not as the user. That way, I can have Crashplan backup my wife's user account and my user account.
Furthermore, you can use the encryption key + a custom password, or your own encryption key with a passphrase. In this case, it is encyrpted locally and the key is not sent to Crashplan[1].
Furthermore, you can use the encryption key + a custom password, or your own encryption key with a passphrase. In this case, it is encyrpted locally and the key is not sent to Crashplan[1].
[1] http://support.crashplan.com/doku.php/recipe/change_security...