The last part you wrote is what I was getting at: you cannot eliminate distributed systems problems from distributed systems. You can only either (a) push them around into different parts of your design or (b) outsource them by using stuff like Amazon's DB-as-a-service stuff. Using immutable objects is (a): now you have a distributed metadata problem.

If they're doing (a) then it's just another Dropbox but with less tolerance for disconnected operation. If they're doing (b) they're just reselling and maybe with a nice client. That's not doomed as a business of course but it's not all that technically interesting.

If there's a (c) it's not in this article.