Now that's a great idea. Have a card that is limited in certain ways: max purchase of, say, $5 (I don't know if $5 will buy anything in $tarbuck$, since I haven

Now that's a great idea. Have a card that is limited in certain ways: max purchase of, say, $5 (I don't know if $5 will buy anything in $tarbuck$, since I haven't been there in many years). Limit purchases to coffee (or tea) only. No transfer allowed from one GC to another. No more than, say, 30 uses per location. It would be an interesting series of social experiments to limit the card in these various ways, and see which limitation helps the uptake, and which hurts it. Fascinating!