Trust would be a better problem to solve then encryption, at least initially. The big problem plenty of people have with email (and for me at least, the phone) is establishing who I'm actually talking to when dealing with a business.
It would be really great if when my bank emailed me, the message was signed with the key they use on their website so we could seamlessly establish that it was really from them.
Unfortunately, banks (at least in The Netherlands) seem to favour a different solution altogether, which is not to send e-mails at all, but expect you to log on frequently on their on-line banking environment to look in your banking 'inbox' there.
Banks, insurance companies, pension funds, the revenue service, the local municipal government; they all expect you to frequently log on to their portals, and look at their digital correspondence addressed to you there. Some do send a notification e-mail stating that 'a message is waiting for you', but you never know if that message is actually important or merely trivial noise. They have declared e-mail dead.
I abhor this situation, because with e-mail (and coincidentally, old-fashioned paper mail) all correspondence addressed to me comes to me in a single inbox, where I can archive and backup important stuff. I really wish I had the option to simply upload my GPG public key to these portals so that all these phony inboxes simply mailed me my correspondence encrypted!
It would be really great if when my bank emailed me, the message was signed with the key they use on their website so we could seamlessly establish that it was really from them.