Yes, I agree, and I invented a Netsubscribe protocol with a similar use. (There is also ActivityPub, but Netsubscribe is much simpler.) (And then there is other stuff where there are already suitable protocols for too, such as SMTP, NNTP, IRC, etc)

DNS absolutely -goes down-, though in much more entertaining ways.

All the DNS in the world can't fail at once. All the Twitter can.

This is because Twitter is centralized.