I'd argue that getting address books to understand what keys are and how to use them would be more impactful. If I put public keys in my address book, which is

I'd argue that getting address books to understand what keys are and how to use them would be more impactful. If I put public keys in my address book, which is nicely integrated with my mail client anyway, then sending encrypted mail should be far more straightforward. The problem then is getting people to use new address books.