Terrifying idea: trusting a third party to maintain the metadata about a key and who's identity it represents.
PGP absolutely got this part right: if you modify the contents of the metadata, the hash changes. Basically, if a private key were to point to Myself, and I distributed it widely, then lost it... an attacker who recovered said key could _transparently_ change the identity of the key and we'd have no record of who was actually correct. And lets not pretend that a government couldn't coerce Github to add an ssh identity to your account (it is owned by Microsoft now, and they have DOD contracts to fulfill).
Keybase solved both these issues: easy and intuitive, transparent proofs, along with the rigidity of metadata with pgp keys: if a key owner changes, the pgp key mutates.