I never knew this...just found it today. Made me giggle.
Payment of sales tax on literature
On 17 January1990 the U.S. Supreme Court made a ruling that sales tax must be paid on religious literature. The following month, a letter from the Watchtower Society went out to all congregations stating that there would no longer be a set price for literature but that they would be given to the public on a donation basis. By way of reason the letter stated that "by adopting a method of literature distribution based completely on donation, Jehovah's people are able to greatly simplify our Bible education work and separate ourselves from those who commercialize religion." They also stated in one of their publications that "there are growing pressures against all religious elements" and that their main concern was to move ahead in the worldwide Kingdom preaching work, "without hindrance".  The Supreme Court ruling was not mentioned.