Fear of empty shelves, coupled with hope for a quick holiday hack, will drive shoppers to grab bunches of gift cards in the next few days.

While gift cards might be simple to buy, though, there are plenty of gotchas to consider along the way and yes, warnings about crime rings running scams.

Like, what happens if the money isn't actually on the card when you try to buy something with it? About 21% of consumers reported that they have given or received a gift card with no money on it, according to an AARP survey of adult consumers.

Sure, some flaky friend could have just given you a gift card that she forgot she used up a year ago. Or the card might not have been activated properly by the retailer. Or you might have ended up the victim of a scam.

Sophisticated scam rings know how to quickly wipe a gift card clean — and gain access to that cash — shortly after the card is purchased by a shopper and activated, according to Kathy Stokes, director of fraud protection for the AARP.

Gift cards can be tampered with at the store, she said, by crooks who grab stacks of cards, remove the security tape from each gift card, and then take photos or write down the card's secret 16-digit activation code.

Many times, the cards don't look like they've been tampered with because new security tape is placed on them. But consumers are warned nonetheless to be on the lookout for signs that someone damaged the card's packaging.

The bad actors, Stokes said, are able to use technology to monitor when the compromised cards are activated. Soon after money is loaded onto the card, the scammers will use the activation code to steal the money. "As soon as that card hits the cash register, they're pinged," Stokes said.

The value of the card can end up being drained by an outsider without ever leaving your hands.

Crooks steal money from gift cards in two ways. One, you could unknowingly be a victim when you buy a compromised card. Two, scammers often impersonate big-name companies or federal agencies as they target their victims. The con artists give you some elaborate song and dance, say frightening you into thinking that you didn't pay your taxes, to drive you to put your money on gift cards to solve some looming problem.

About one in four people who report losing money to fraud, according to the Federal Trade Commission, say it happened when a scammer tricked them into giving the numbers on the back of a gift card.

During the first nine months of this year, nearly 40,000 consumers reported losing what adds up to $148 million in scams where gift cards were used, according to new report by the Federal Trade Commission.

Oddly enough, Target is a big name that's popping up. The FTC noted that scammers are increasingly demanding Target gift cards, which proved to be the most popular choice based on reports received by the FTC during the first nine months of this year.

"Target gift cards accounted for about $35 million in payments to scammers," the FTC said, "more than twice as much as any other brand of gift cards."

The median amount lost when consumers paid with Target gift cards was $2,500. And 30% of people who paid with a Target card said they lost $5,000 or more.

Target said in a statement that it has increased in-store signage to warn customers of common gift card scams and educated employees to keep an "eye out for potentially distressed guests buying gift cards and intervene as needed."

"We also continue to implement new technology to prevent gift cards from being abused by fraudsters," Target said in a statement.

According to the FTC, scammers are demanding specific gift cards: Target, Google Play gift cards, followed by Apple, eBay, and Walmart cards.

Scammers often direct their victims to specific stores to buy the gift cards: Target, Walmart, Best Buy, CVS and Walgreens. Any time someone demands that you pay for something with a gift card, Stokes said, you can be 100% certain that it's a scam.

Susan Tompor is the personal finance columnist for the Detroit Free Press.