Very sensible design decisions and it's hard not to get excited about Rob Pike's involvement. I think Dat confers significant advantage by being hostless, but with Google's name behind it, you never know where Upspin could go. We have plans for secure key-distribution via Dat that's similar to Key Transparency, but it'll take us a couple months to a year to implement it. I feel bad for the Keybase team right now, that's for sure.