I have often wondered it a cash card like a telephone card would be possible or practical. You could buy it the same way you would buy a Money Order but use it to make purchases like a credit card. Since there is no identifying information it would be quite anonymous. The seller would be assured of his money and the buyer of his privacy.
a.cricket
You ought to be able just to pop in a 3.5" floppy with some digital cash and go shopping.....