[jschlatter]

> They have the technical means to control what goes on there or not.

They have less control than you may think.

Any ethereum miners (or proof-of-stake validators) who block some class of transactions immediately become vulnerable to denial of service attacks.

This came up back in 2016 with the DAO hack on ethereum[1]. Some ethereum miners considered blocking transactions that moved the stolen funds, but then realized that this was infeasible: if you block such transactions, then the DAO hacker can spam you with them. Such spam on ethereum is usually prevented by requiring the sender to spend money on each transaction (ie pay gas fees). But that fee is only charged when the transaction is included in a block -- if you refuse to include it, then the spammer pays nothing. The kicker is that, by Rice's theorem, there is no way in general to distinguish "malicious" transactions from non-malicious ones (for _any_ definition of "malicious") short of just executing them to see what they do.

So if you as an ethereum miner (or validator) try to block certain transactions, you can be forced to do unbounded amounts of work for free, ie DoS'd.

[1] https://hackingdistributed.com/2016/07/05/eth-is-more-resili...