Wow, this has been around for awhile. Pretty interesting take on this in the link to Brad Fitzpatrick's article from 2007.
Your statement about companies being unmotivated to support anything like this rings true to me. It is exactly what I would expect. The question is, what might motivate them.
Proof that it works, that it can lead to customers migrating in. Or some kind of legislation. Main point is for it to work though.
Personally, I'm waiting for some combo of SOLID, the Fediverse and Matrix. SOLID is like FOAF and XFN and *dav and etc on steroids, very JS orientated though and not the most friendly of UX.
