In 1971, a group of experts concluded that a digital payment system that tracks people would be the most effective but unobtrusive system they could imagine for a dictatorship. ( pages 10-11 of this pdf , or search for "Electronic Funds Transfer Systems" in this plaintext version )

Now that exists, we see it is indeed ideal for that purpose. So join me in promoting the use of cash -- by insisting on paying cash, and telling businesses "No cash? No sale."