> Key exchange between people should always require some kind of offline verification. If you don't do this, you can't really trust that the person you're communicating with is who they say they are.

I know a lot of people who I've never met IRL and likely never will. When you think about it, I already don't know that they are who they say they are.

Many of them live far from me. I don't see a practical way to exchange keys with them offline. You have to travel and do it face to face, or trust that USPS, UPS or FEDEX haven't been compromised. Sure, that's very unlikely for Joe Blow, but still, you're doing it offline for security.

Lastpass and probably others have an online secure exchange tool, but then you have to trust Lastpass (which I currently do, if very uneasily).