Exactly. I could see a government, in need of tax revenue, enacting a law that taxes some activity, then going after people that have been doing it for years.

Suddenly, we owe ten years of back taxes, with penalties.

It’s not feasible to do this.

But there are plenty if people –many on this very forum, I suspect– that know what they are doing is highly immoral, and will likely get shut down, but … MONEY … so they do it for as long as they can gt away with it.