It's unfortunate that simple public key encryption, which has been easily available for many years, is still seen as untenable and "super-paranoid." Any email client, or better yet Gmail, could easily implement it and make it virtually transparent to the user (when both ends of the email are using such a client, obviously).
I apologise if you have mistaken my meaning! I certainly hope we don't take wider scale encryption to be untenable, but it is very certainly untenable for a single person to use the web in a meaningful way with normal people while maintaining that every single email needs to be encrypted.
