@ewok@cybre.space
Its client is open source, server side isn't. Privacy policy is clear on what is done with data: https://keybase.io/docs/privacypolicy
Imo they are good for keeping not so sensitive data if your main purpose is storage. Main purpose of service is public proofs of identites and thats why I think they are useful. Lesser known fact is that you can host static site on Keybase public folder, one more neat feature.