When you think of fraud, you might think of large, high-profile cases like headphone giant Monster suing Beats for millions of dollars, or hedge fund managers getting convicted in court. It might surprise you that, according to Visa, online merchants lost $11.8 billion to cases of "friendly fraud" in 2012. This is where a customer issues a chargeback (in some cases deliberately), claiming an item was never received or that they never made the charge.

As many of you know, I have had a few e-commerce companies of my own. Most recently, I was the owner of Organize.com, doing $10 million a year in online sales. Friendly fraud was something we had to deal with on a daily basis. What happens is a customer orders products from our store, then, on the last day to return, files a claim with Visa or a similar card service. The customer claims that the product was never received (though we have proof through shipping tracking). The case is filed, and we have to give proof. It's a bit of work, and hurts our merchant account every time this happens. Typically, funds are put on hold as well, which can really hurt a company if it's having cash-flow issues. It's our word versus the customers, which means the customer typically wins. At Organize.com, we figured around one in every 300 orders would involve friendly fraud.

The problem has gotten steadily worse since Visa's reported data, with a report by CBS finding that over 86 percent of customer chargebacks are deliberate. According to CBS, the steps to investigate a chargeback are "tedious and labor-intensive," citing Visa's own chargeback management guide.

Last week, Trustev, an e-commerce anti-fraud company, ran a study of that found that 17 percent of American consumers have disputed charges without contacting the online merchant. The scarier fact of the 1,000-person study was that 5.1 percent of those people admitted to deliberate chargebacks, with more than 20 percent saying that it "didn't bother them very much" or that it was "OK."

"In some cases, the consumer forgets which charges he made, and in some, he's intentionally committing fraud," Morgan Quinn from GoBankingRates.com writes in the Las Vegas Review-Journal. It's a gradual, almost imperceptibly difficult problem, as customers accidentally or deliberately chip away at companies in amounts as small as $5 at a time.

However, Trustev's study found that 8.6 percent of the people who had deliberately committed friendly fraud did so with items costing over $100 each. "Friendly fraud is a big problem for retailers, and it's very hard to combat, as these are 'good' customers without traditional fraud red flags," says Pat Phelan, CEO of Trustev. The company attempts to combat friendly fraud by tying repeat returners across multiple vendors on its network, along with tracking actual deliveries to customers' profiles.

ChargeBacks911, a company founded to fight for merchants hit by friendly fraud, has a comprehensive guide to protecting yourself. While many of the tips are obvious--such as keeping records of IPs and transaction histories, and making sure the customer is aware of the terms and conditions of sale--they also recommend a more loving, educational approach. This means that you should, ideally, keep the customer well-informed about the purchase so that they're less likely to "make the mistake," or at least be more loyal to your company.

A piece by Brian Krinch, a senior partner for credit score company FICO, also attributes the problem to trust between the consumer and the vendor--and says that the person in question may simply be too embarrassed to admit their own fault. "The best defense here is advanced consumer education," Krinch writes. "Consumers can also be wary of revealing their own actions and naivety: Imagine being asked by your bank, after a case of fraud, 'Have you ever allowed someone to have access to your card, or written down or revealed your PIN number?' Instinctively, everyone says, 'No, of course not' for fear of criticism or reprisal--in fact, many people do exactly that."

In any case, be intimately aware of your customers. Don't treat them as guilty until proven innocent, but be wary of any new customers suddenly making wild purchases that mysteriously disappeared. Especially when UPS says otherwise.