One of the issues with Public Key Infrastructure (PKI) has always been a way to safely store and backup the private keys. Most of the time this is done by using a keydatabase for storing the keys or even an HSM in larger organizations. And the only backup solution I encountered so far was burning the key to a CD-R or storing it on an USB stick and putting them in a (physical) vault, controlled by the Security Office.
I have a smarter idea for offline backups!