> But an across-the-board price increase hardly seems fair. Those abiding by Walmart’s rules are being asked to make up for a shortfall that is entirely the fault of suit-stealing rule breakers. Honest shoppers who don’t generally like to use invisible suits will be particularly furious — and who can blame them? They are being asked to pay more for the goods they hold dear in order to support the use of a single product they never cared for much anyway.

The generic form of this argument is that you put a tax on stealing in general. But we already have that; it's the laws against stealing (or tax evasion).

Obviously you can still be caught for tax evasion even if you're using cash. The counterparty can report you and the IRS pays rewards for that sort of thing. Law enforcement can notice that you're living in a mansion and have six cars while reporting no income and investigate how you're paying for it. Moreover, that puts the cost on the people actually evading taxes, instead of on all the innocent people using the anonymous payment method. And isn't the point here supposed to be to not impose costs on innocent people, and to deter tax evasion rather than deterring privacy?

Also notice that even the proposed system already exists. If you have digital money in a bank you get interest (CD rates currently ~5% APY), if you have cash in a mattress you don't. But people using cash to evade taxes don't have to stick it in a mattress anyway; they can just spend it immediately, which is what they already do because of the existing incentives.