Does it not work at all - anywhere? 7 day (unlimited) passes can only be used once at any one location within a short time frame, I think it's ten minutes or so. The card becomes invalid at that reader for that short time, but it can be used elsewhere immediately.

This is so you don't "swipe in" your entire group with only one unlimited card - each person must have a card. Also, trains to the airport require a "cash value" card - unlimited cards don't work on the JFK airtrain.

On the other hand, cards with cash value can be used up to four times at once (e.g. a family of four) and value is deducted with each swipe.

The unlimited card is a better value for tourists - but check swipes at self service readers reveal only the expiration date.

It is true, if the card is defective, you must send it in to get the refund.