Integrate it in an e-mail service that is very popular like Gmail, lead everyone through an initial set-up to create their public keys, and then tie that key to their profile. Then you won't have to know anyone's public key anymore, and everyone would be using PGP by default.
The only issue is that Google would have to ensure you're creating the private key as "locally" and securely as possible, without them being able to copy that key to their servers when they're creating them. That might be very tricky, while still remaining convenient, and they may have to allow for independent audits so we can make sure they aren't transmitting the data.
The only issue is that Google would have to ensure you're creating the private key as "locally" and securely as possible, without them being able to copy that key to their servers when they're creating them. That might be very tricky, while still remaining convenient, and they may have to allow for independent audits so we can make sure they aren't transmitting the data.