Checked out Dat and Beaker, and I'm in love already - it's great to see people appreciating the terrible costs of the blockchain, and figuring out how to get distributed trust without it.
The post by Beaker's creator, linked in this article, is also worth a look: https://pfrazee.github.io/blog/secure-ledgers-dont-require-p....
Keybase is a good example of the centralized “secure ledger” described in the article you linked:
> Keybase's approach to server security: (1) each user has his or her own signature chain that grows monotonically with each announcement; (2) the server maintains a global Merkle Tree that covers all signature chains; and (3) the server signs and publishes the root of the Merkle Tree with every new user signature. This configuration strongly discourages the server from lying by omission, since clients have the tools to catch the server in the act.
Source: https://keybase.io/docs/server_security/merkle_root_in_bitco...
Beaker is interesting because it's enabling things that aren't possible on the HTTP web, and (again) focusing on making it stupid easy for non-tech people do things. Meanwhile, the major browser vendors' idea of forward motion amounts to working on things that web developers can use to impress other web developers and maintaining existing barriers to entry.