[delusional]

An important part of keybase is that all proofs are publicly verifiable. When i prove i own a github account, I have to post a public gist. When you get my key from keybase, your client automatically looks at that link and verifies that the gist, and the text within (which is signed by my key) is valid.

Keybase is just the place that connects all the proofs. The actual client verifies that they are correct. As such, if keybase was every compromised they would only be able to change the link to the gist, which wouldn't do them much good without access to my github account.