Pretty much everyone uses this policy now- for that, I can't find one single store that issues gift "certificates", instead of the electronic gift cards you're all talking about.
Seems like a lot of ranting over something simple. It's money to be spent IN THAT STORE. You bought it WITH THE EXPRESS PURPOSE AND INTENT of using the FULL AMOUNT of the balance IN THAT STORE. Just because what you purchase isn't enough to kill the balance doesn't mean you have room to gripe.
And who cares if you have to pay the difference in your own money if the purchase is more than the card? You had to do that with the almighty "certificate" everyone's chatting up.
Bottom line is: It's credit for THAT STORE. You knew that when you bought it, or when you received it as a present. You can't suddenly decide, "oh i think i'll take some money from these people and spend it elsewhere".
p.s.- I've never had a complaint about such a thing at my workplace, so I'm not bitter or anything. Just one man's opinion.
Fire at will.