Or someone knowing you book a lot of hotels and flights, so your home must be empty a lot.

The thing about Ethereum's public ledger approach is that it enables a lot of features - broadly advertised smart contracts, for example. Tornado.cash is literally an attempt to replicate the privacy benefits of ZCash inside of Ethereum's generalized blockchain. From a computing perspective that's quite interesting - you start with a public system and find a way to emulate a privacy within it.

It's not hard to imagine that the end goal is CBDCs having a monopoly on legal privacy. (Privacy from your neighbor, not your government.)

It also doesn’t follow that a private ledger would be banned any more than, say, credit cards or PayPal are banned. The thing which would get them banned would be refusing to comply with KYC laws, which is a political choice rather than a requirement.

It remains to be seen what they mean by this. Tornado doesn't extract fees, so the profiting couldn't be exactly direct.

> It also doesn’t follow that a private ledger would be banned any more than, say, credit cards or PayPal are banned.

I specifically said "fully private", not "private from your neighbor", to differentiate with credit cards or PayPal where users have no transparency or control over who sees their data.

> The thing which would get them banned would be refusing to comply with KYC laws, which is a political choice rather than a requirement.

It's not possible for a decentralized system to "comply with KYC laws". That's like asking that paper dollars require an ID to transfer. They can't do that, they are bits of paper existing in physical reality.

Similarly, autonomous consensus-based systems like cryptocurrencies and trustless smart contracts can't just say to users "sorry, I'm not able to serve you until I see your valid government-approved ID", they are "things" not "services with a helpdesk, a street address and a CEO".