Not only is cash a crime, as in cases like Kent Hovind’s, so is exercising your right to free speech.
Irwin Schiff ultimately received the life in prison for speaking out against the IRS and the tax system. From Mises.org:
Irwin Schiff, imprisoned for his resistance to the federal income tax, died yesterday. Efforts by his son, the noted financial commentator Peter Schiff, to secure his release from prison so that he could die with his family, were unsuccessful. Schiff’s sad passing illustrates an essential truth about the state: if you resist its orders, you will be dealt with by force.