At first glance, what’s not to like – a thought through JSON api which uses HTTP PATCH – see that proves they’ve been thinking.
Unfortunately it repeats what I believe is the big mistake in OpenID – assuming that HTTP URLs (and in the end DNS) is the right place to root the decentralisation.
OpenID proved that most people won’t register a domain and set up a service on it just to have an identity on-line (and arguably that they just don’t think of themselves as URLs). And if you don’t do that, you’re still tied to whichever host you initially choose. You might have data portability, but you don’t have identity/graph portability. Even with e-mail (one of the 2 obviously successful internet-scale decentralised systems), most people only have data portability and not identity portability because they don’t own the domain they’re sitting on. That massively increases the costs of moving, and I’d argue moving e-mail providers is easier that moving social graphs because of the variety of relationships and associated data you have with people in your social graph.
So can/how do we do a social network/graph/identity system where everything isn’t tied to URLs/DNS?
Having given it a full couple of hours though, I think it’s possible with judicious use of crypto, really good UX, and probably some help from the smart devices everyone carries around.