I spent about 2 years harping on everyone I know to use this, including clients, bosses, friends, colleagues, and everyone else I would send more than 2 or 3 emails. I was only able to get a couple of people using it (and that was probably mostly because they were worried I would be able to get them fired if they didn't keep me happy). I eventually gave up.

Crypto is super important, but it's way too hard to get practically anyone, even technical people, to use it. This area is ripe for disruption I think, especially as more and more high-profile leaks get released. Someone could sell some great, easyish-to-use crypto software and get a lot of money.