I can't say whether his implementation makes sense. Regardless, I would like to see public key encryption of all email. There's no reason why messages should be plain text anywhere except at the two ends. I realize key management would be a problem, but it's probably a solvable problem. The solution would have to allow most people to be practically unaware of encryption issues.
Encryption of all email would make intermediary virus scanning impossible and spam scanning next to impossible.
Wouldn't it make spam impractical because you would all of a sudden need much more processing power to encrypt the messages (especially millions of them)?