I agree with the sentiment and I wouldn't call Bluesky "open social"- I don't trust them either. But I still don't find these to be arguments to be against the protocol per se, which I find really interesting.

> Who holds the keys to the kingdom? In this respect, I think the AT Protocol fails spectacularly, mainly due to the lack of a credible strategy to implement really self-custodian identities

From what I've read, you can still own the entire stack from top to bottom, none of it is necessarily tied to bluesky. Even the identity managed being discussed only applies to bluesky, and whatever ecosystem subscribed to it; but in theory, you could create your own social platform with a new one (you'd obviously lose that ecosystem). But then again, this would also apply to Mastodon, since whoever owns the instance could always nuke it, and if you own your own instance, you need to build an network that trusts you. There's always an authority involved.

> The difference being, last time I checked (and of course things might have changed in the meantime) with AT Protocol it was only possible to self-host part of the infrastructure (and hosting the relay is insanely demanding).

Well it's definitely not the "50TB" you mentioned e.g here is someone running a relay on a $34/month vps and isn't going to accumulate more disk: https://whtwnd.com/bnewbold.net/3lo7a2a4qxg2l But it's importance is overblown anyway, it's just a json transmitter for signed data. I think the pds and identity managements are the better concern, and I hope there's a better way to decentralize those (if that makes sense).

EDIT: You're still correct that to fully spin up a new bluesky on your own you'd need an insane amount of storage for hosting all that data that's currently stored on bluesky (especially the did:plc and pds). All good arguments against the company, but that's only because people are choosing to store their pds repositories on bluesky. You could just as well point your repo to your own server and use a different social media. They could go under and someone else can create a new app view. I find that really cool; still leaves the identity issue open.