What's happening?

Flashbots is currently the most used MEV-relay available to Ethereum validators. It has a literal chokehold on Ethereum, making up 73% of all MEV-relayed blocks, and 42% of all blocks.

Non-OFAC compliant transactions (such as to sanctioned addresses, e.g. Tornado Cash) are and will be rejected by these validators outsourcing their block production to Flashbots and other regulated relays. However, I am focusing specifically on Flashbots because of the scary dominance it has over other MEV relays.

Why should I change relays?

Same profit, more censorship resistance. If you're only a validator for the money and do not care about the health of the network at all, then pull your money out (after shanghai lol) and stop centralizing the network.

Is it really that bad?

For now, not so much, because it'll just take 24 seconds instead of the usual 12 for a censored tx to go through. But if people keep defaulting to Flashbots as their MEV-relay, then it could be a problem over time, or at least until proposer-builder separation is added to the Ethereum protocol.

Hasn't something like this already happened?

Sort of, but on a more technical level.

Ethereum is made up of clients. Clients are the way nodes and validators interact with the network, and there are a variety of choices for both execution (handling transactions and blockchain changes) and consensus (transaction ordering) clients. The most known is geth, which also has a software monopoly over the network. It makes up 77% of execution clients, which means if geth ever bugs out and forks the network, 77% of the network will be seen as 'malicious' by the Ethereum protocol, and therefore slashed should they return to the main chain.

TL;DR

Flashbots, a censoring relay, has a chokehold over the Ethereum network. Please change your relay if you truly care about the network's health and overall censorship resistance.