Loren Berlin is a columnist at DailyFinance.com . She can be reached at loren.berlin@teamaol.com. You can follow her on Twitter @LorenBerlin, and become a fan on Facebook.

Once upon a time, American Express 's fabled "Black Card," reserved for the world's wealthiest and most elite, was just that -- a fable, an urban myth. But not anymore.Elizabeth Crosta, director of public affairs at American Express ( AXP ), confirms that yes, the Centurion Card , as it's officially named, exists, and is thriving despite the larger economic troubles. "We're actually seeing a rise in luxury spending," she explained. "Our premium customers are definitely spending more and traveling more than they were a year ago."Interestingly, the myth predated the card. Doug Smith, director of American Express Europe, told snopes.com , "There had been rumors going around that we had this ultra-exclusive black card for elite customers. It wasn't true, but we decided to capitalize on the idea anyway. So far we've had a customer buy a Bentley and another charter a jet." (Yes, someone bought a Bentley -- a car that costs between $200,000 and $400,000 -- with a charge card!)In general, I try not to get too nosy about the lives of the very rich, in part because I get a little jealous, and in part because I get a little distressed about wealth disparities. But this time, I couldn't resist. I wanted to know more, both about the fanciest of fancy cards, and the spending habits of the uber-wealthy.The Centurion Card, which really is all black, and made of titanium, was introduced in 1999 and is extended to consumers on an invite-only basis. According to Crosta, there is no formula for qualifying. "It's decided person by person," she says, before adding with a chuckle, "I haven't been invited. I know that...People will call us and ask to be invited." Nonetheless, the Internet is teeming with speculation about the requirements. The general consensus is that eligibility involves some combination of a stellar credit score , a minimum of $250,000 a year – or roughly $21,000 a month – in charges , and at least one year's history as an American Express cardholder, as well as significant net worth.American Express is tight lipped on the details. Crosta confirmed that there is a one-time, $5,000 initiation fee, and a $2,500 annual fee. However, she wouldn't disclose information around the percentage of selected consumers that accept the invitation, the size of -- and events that trigger -- a late fee, whether invitations are mailed or delivered by hand (as many on the Internet speculate), or the number of Centurion Card-carrying customers. "We cannot provide the exact numbers," Crosta said, "but I can tell you the demand for the Centurion Card continues to be high, as it provides a rich suite of benefits that one could not replicate on their own."American Express has tried to keep those benefits under wraps as well, but some details have seeped out. Known benefits include what you might expect for an affluent population that frequently travels -- airline and hotel upgrades, and access to those nice airline lounges at airports. But for many cardholders -- who have their own jets and multiple homes scattered around the globe -- these may or may not even count as perks. Rather, the real benefit comes in the form of the 24-hour concierge service that can secure tickets to sold-out music and sporting events, that will do your shopping (if you so desire), remind you of birthdays and anniversaries, and find that impossible-to-locate, limited-edition collector's item.According to snopes.com, the concierge service has located, purchased and delivered to Europe the horse ridden by Kevin Costner in Dances with Wolves, gathered sand from the Dead Sea and had it couriered to London for a child's school project on the Holy Land, and arranged for an aspiring actress to audition for a soap opera. Other benefits include access to the company's area at Fashion Week, and invitations to a $3,600-per-person-per-night weekend at Pebble Beach, hosted by Rolls-Royce Not surprisingly, American Express is equally demure regarding who, exactly, has a Centurion Card. Based on my Internet trolling, it seems to me that customers with the business version of the card -- that is, they can use it for their company expenses, as opposed to their personal needs -- are very willing to disclose their status symbol. But those at the highest echelon -- the few with the personal card -- prefer to stay in the shadows. I only located two instances of personal card-holders who went on the record about the card in a legitimate publication: Billionaire entrepreneur Mark Cuban , and millionaire mogul Giovanni Zampolli So how do these super-rich clients handle the power of the Black Card? Do they just make minimum payments and roll over the debt? Surprisingly, no. The Centurion Card is a charge card, not a credit card, which means the balance must be paid in full every month. Crosta explains, "There are no pre-set spending limits ... but because you have to pay it in full every month, it's up to the cardholder themselves to decide how to use it."That may be one of the secrets to the success of the world's wealthiest: They pay off their plastic in full every month. In other words, they live within their means, which is a great approach to managing your finances, whether "your means" enable you to buy a Bentley, or just pay the $10 admission fee to see one at a car show