The holidays may be over, but chances are you've got a constant reminder: a gift card. Gift cards are always a popular choice for holiday gifts, so you'd think more of them would actually be redeemed -- but experts believe at least $2 billion worth of the cards given last year will never see a cash register.

So what happens to all that money?

That $2 billion figure may seem high, but it's less than it was back in 2007, when $2.6 billion was lost to fees alone, with another $3.5 billion disappearing because the gift cards expired.

Subsequent changes to gift card laws have meant most fees and expiration dates no longer apply, but there's still a big pool of cash left untouched because people simply forget about the cards, lose them, or find there's nothing they want from the card-issuing stores.

In years past, retailers claimed that money as pure profit. These days, some states intervene and seize the funds themselves after a certain period of time, which means consumers have to go through their state treasurer if they want the gift value back.

Most, though, don't do so -- as of 2008, New York state had taken in $9.6 million in unclaimed gift card money, but distributed only $2,150 back to consumers. And the Pennsylvania attorney general's website claims it's in possession of "more than $2.7 million in unredeemed gift certificates and is currently seeking the rightful owners."

Brian Riley, a senior research director in the retail banking and cards practice at TowerGroup, doesn't like either approach. "From the way I look at it, it's the consumers' money," he said. "The whole nature of gift cards is that you are tendering money to retailers and asking them to hold onto it until you are ready to use it. Just because you haven't used it doesn't mean it's no longer yours."

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