Trying out Keybase

My understanding is that the passphrase is the key to your private key, as well as the api login for keybase.io, and that it's never sent to the server.

Now, one may question the encryption method(s) on the API and the private key stored encrypted on keybase, I also believe you don't have to upload your private key. That said, part of the advantage of keybase is the ability to access it from "anywhere". In this case ease of use is more paramount. Also, being able to regularly validate an email address would be nice as well, I think there's been progress on this. Also, that one should be able to easily integrate with email applications for more transparent key lookups for encryption... now, there may be issues of mitm at one's email service (if web integration), but getting people to use encrypted messaging has always been the harder part of adoption, which keybase is a part of.