We are also thinking about offline ways to share the key such that the centralized side is not required - eg. a QR code displayed on one device and scanned by another to propagate the wallet. This creates a problem if a user loses all of their devices though.
I'm part of the team that develops the Embark Framework and it would be awesome to rehash our decentralized Reddit tutorial using a fully decentralized Hedgehog.
https://embark.status.im/news/2019/02/04/building-a-decentra...
As for the QR code getting lost, that's a good point, but the user could always be encouraged to make a physical copy and keep it in a desk drawer, and/or store it electronically somewhere else (e.g. Dropbox or 1Password) "just in case".
We did not want to require use of Keybase to use our dapp Audius, though I could see it making a lot of sense to offer a keybase integration as a potential option.
FWIW, Audius still supports Metamask too - web3 is all about giving users choice from our perspective.