Per snopes this is true, however they have a pretty detailed explanation as to how this is done. NFA you are correct, the PIN plays a role in this so be sure to check and see that the pin has not been revealed on the back of the card when you purchase it.
http://www.snopes.com/fraud/sales/giftcard.asp
"Cheshire Puss," she began, rather timidly... "Would you tell me, please, which way I ought to go from here?"
"That depends a good deal on where you want to get to," said the Cat.
"I don't much care where..." said Alice.
"Then it doesn't matter which way you go," said the Cat.
Alice’s Adventures in Wonderland