I like to insist that the PLC Directory collects and distributes updates to highlight how it's different from a database. The latest state of the account is signed by the key that created it, or by a key that succeeded it. The directory can't inject any values, it's just a low-complexity solution for data availability: the "how do I learn about updates" part.

It could decide to hide/reject updates, but then it could just as well be forked and replaced if it did that. If downstream applications decide to get their account updates somewhere else, that's the directory now, without any loss of continuity for the accounts.

You don't get that from a simple database.

One could argue domain registrations, and so did:web, are more of a database controlled by a (large, international) organization than PLC. Plenty of tradeoffs of course.

PLC is imperfect, like every solution to identity so far, but it's a lot better (in terms of ownership / control of your own ID) than DNS.

I think a model where public really means public and private means private is more clear to users than a closed platform where neither is true. Facebook is actively using your private posts for ad targeting and they can remove your public content at any time for no reason. With atproto that can only happen if you pick a bad hosted PDS out of many.