The problem of course is enforcement. Contributions are still anonymous." From Sir82's post.
When I was in I always contributed by check, so it sure wasn't anonymous for me. I did so in order to have proof of my charitable deduction on my income taxes each year for the IRS, just in case I ever got audited. I never made (or make) any contributions to charitable institutions in cash unless I am able to get a receipt.
Speaking in generalities, if the "average" Witness is making minimum wage or less, then it probably wouldn't benefit them to itemize their deductions on U.S. Federal Form 1040 Schedule A - they wouldn't have enough itemizable deductions to exceed the "standard deduction." But in the USA I think there are a lot of witnesses like me (when I was still in) -- owns a home, pays high property taxes and state income taxes-- all of which are deductible on Schedule A, so that my total deductions on Schedule A were much higher than the "standard deduction." I believe the mean wages in the USA today is around $45,000 (may be off by a few thousand). Ten percent of that figure would be a whopping $4,500 and if Average Witness earns the mean wage and was "guilted" into contributing the full 10%, that would reduce his or her net taxable income on Form 1040 by a large amount if that amount, combined with other items deductible on Schedule A, would push them over the amount of the "standard deduction."
That raises all sorts of interesting scenarios. When I was a Catholic the church used the "envelope" method of keeping track of who donated how much cash (with your name and member number pre-printed on it), if a parishoner did not contribute by check. It would be easy enough for the FDS slave to claim new light and have every congregation start handing out a year's supply of pre-printed envelopes to each family. Then the elders and NY would know EXACTLY how much each family/member was contributing.