Right. I don't even understand why this article had to be this verbose. It's not like we need to be "convinced" that local is better. Everybody who values privacy and independence knows already. But this stuff is unimplementable -- we suffer from the cloud disease because it's immensely profitable for the cloud providers and cloud-based app providers to enslave us, and to bleed us out. Their whole point is locking us in.
"Sharing models" are totally irrelevant until the concept of self-determination is tolerated by the powerful (and they will never tolerate it). Accessing my data from multiple devices is totally secondary; I don't trust mobile endpoints to access my remote data in the first place.