Nice Article. You may also want to include link encryption and even network-wide encryption. You touched on it a bit with email encryption but many companies move data around with applications other than email and are prone to the same vulnerabilities.

Link encryption has often been looked down on by network people because the exchanging of encryption keys between the source and destination forced a static path or tunnel through the network, The network folks do not like this because many applications such as Voice over IP (VoIP) perform best when the network can route packets dynamically. Encryption also becomes very complicated when more than a few links are encrypted. Fortunately, there are now technologies available that allow all the traffic on the network to be encrypted without impacting applications and without increasing network complexity.

With this new technology companies can easily encrypt all of their traffic on the network making it immune to hacking, intrusion or inspection.