Bluesky is a purportedly-decentralized social media company that spun out of Twitter, beginning in 2019. It makes sense that people are hunting for new social media platforms right now — Elon Musk's disastrous takeover of Twitter has demonstrated how fragile relying on private VC-funded companies is for something so critical as communication infrastructure. BlueSky's answer to this is that they are decentralized — thanks to the AT Protocol, anyone can run a server. Unfortunately, it's decentralized in name only:

• The AT Protocol is entirely controlled by Bluesky the company, with no community governance structure or plans for a governance structure. Want to change how it works? Tough luck, buddy.
• Want to run a server yourself? Well, the server is closed-source, so you'd better enjoy reimplementing it all yourself.1 (Edit: I'm told that this is not true, and that the atproto has the server code. However, it's unclear to me how much of what's running on bsky.social is public — the identity parts appear to be, but not the web frontend, that I can find.)
• The apps? Also closed source, you don't have any control over them.2

This isn't how you build a decentralized ecosystem, it's how you build a system that you can claim is decentralized while still holding all the power yourself.

There's a lot more that's wrong with Bluesky that I'm not going to get into, since I honestly don't really care. But if you care about not giving more power in your life to a VC-funded company started by a guy who said that "Elon is the singular solution I trust" to running Twitter, you probably want to stay away from Bluesky.