I got lazy and sloppy; tried a mastecard from a grocery store a couple blocks away, instead of re-loading a visa card at walmart a couple miles away.
I'd buy cheap dvds off amazon, make sure to count the sale and postage---but the final sale wouldn't go through; amazon would e-mail about, seemingly, not enough money on the card.
I bought one or two cards to make sure my amazon account not ruined by buying and then having to cancel stuff. I bought a 50 and two 25 dollars cards----I probably lost 30 dollars total.
And when some amazon seller listed merchandize that was sold a long time prior, my money wasn't refunded with Mastercard either.
I used up these cards in a day or two, wasn't as though they were laying around forever; mastercard must deduct fees right on the same day, on top of the five dollars you pay for the card.