Even though it's by the creator of Jabber, it's not about streaming XML stanzas, thank you very much.
Locker seems to run on the server, using node.js, so until everyone of us has their FreedomBox plugged in, this will not really give us freedom.
What if we ran this in the browser, using client-local storage? And then, as Dave Winer would tell us, we push that stuff as RSS, err, Atom feeds, maybe connected using Atom Paging and Archiving, to a dumb cloud store, hopefully free as in freedom? (This is where Content-centric networking comes in, as a simple way to dedup, among other awesomeness.)
Doing the crawling of a user's feeds in the browser has the big benefit that we have cycles to burn and bandwidth to waste there. Scalable following is damn hard, which can be seen from the fact that it's one of the few algorithms that's not provided as a shrink-wrapped, commoditized package. Yet.
The second piece I find wildly interesting is homomorphic encryption. As far as I can tell, the promise of homomorphic encryption re cloud storage is that the cloud store can sort and search encrypted data. I.e., data it can't even look at can still be subjected to the Big Data treatment, aka Google's infinitely-scalable b-tree. (Links: Order-preserving Encryption, Cryptographic Constructions for Secure, Privacy-preserving Distributed Information Sharing.)
Of course, if we want to do to microdata and the web what Emacs did to plain text and Unix, first we need a real Lisp in the browser. Thankfully, that's exactly what I'm working on at the moment. Stay tuned.