Heh, last summer I walked 20 miles down the highway to a neighbouring town just to say I did.

True but would you want it to be illegal if the vast majority people that did walk 200 miles on foot instead of driving, did it because they were doing it to get away with committing a crime?

I would not want walking far on foot to be illegal just because most people who actually did that were doing so to further a criminal goal, no. That is how we slide into authoritarianism.

It's the same reason I want a right to privacy; you could argue that most people who want to hide something from the state want it because they're doing something illegal, but I still find it valuable that I can do things without being tracked. It's the same as the right to go outside without any form of ID; most people who aren't up to anything illegal could make sure to always bring valid ID at all times, but I value the freedom to not be forced by the state to bring something. It's the same reason I would oppose a law that you must wear a GPS tracking device on you at all times; most people do it willingly with their phone and watch these days, and the only people the law would really affect would be criminals, but I value the freedom to go somewhere without being tracked.

I currently make all payments electronically, but I value the freedom to be able to transfer money without leaving traces of the transaction, even though I don't currently exercise that freedom. Because the state doesn't have any business micro-managing individuals' behaviour like that.

So make the criminal act at the end of the journey illegal, not the act of walking 200 miles on foot.

This feels like the question of Blackstone’s ratio: “It is better that ten guilty persons escape than that one innocent suffer.” I’m not an absolutist about these things, but I take Blackstone’s side of this (very difficult) question.

Is that ratio a target? I thought it was a kind of hyperbole. There probably are places where more than one in 10 people are laundering money.

Would you want the internet to be banned, because people are using it to get away with committing a crime?

Would I want certain things on the internet to be illegal, yes. Like they already are.

I'm not sold that the majority who pay in cash are doing it to get away with a crime.