What's Gilt Groupe's secret weapon?

	The company's most valuable asset might not be its ability to convince consumers to buy tons of fancy retail, but rather its ability to watch how they do it. FORTUNE -- It would take a secret weapon to start a successful print publication from scratch right now. That's why the partnership announced last week between high-end online retailer Gilt Groupe and a new luxury magazine called Du Jour has raised many an eyebrow. What, exactly, is in this for Gilt, especially given the turbulent status of the magazine business? On the flip side, how would a partnership with an online sales site benefit a magazine? Gilt Groupe is known for selling luxury items -- some of them at a discount, some not -- via a method called flash sales. Online flash sales offer select inventory at a certain time daily, and items often run out quickly. It has enabled Gilt to use the strengths of the web to sell products to that coveted slice of consumers with the budget to view a $2,000 dress, down from $4,000, as a steal. But there is more to Gilt than capitalizing off of flash sales, CEO Kevin Ryan insists. In fact, the company's most valuable asset might not be its ability to convince consumers to buy tons of fancy retail, but rather its ability to know precisely who is purchasing and how. The flash sale model was fueled by an excess of inventory at luxury retailers who were hit by a slowdown in consumer spending during the recession. Gilt helped pick up the slack, offering high-end items at a discount on an attractive platform. But luxury retailers have gotten better at streamlining their inventory, cutting into the glut of high-end items to push to sites such as Gilt. MORE: Web advertising's master auctioneers But Gilt CEO Ryan isn't troubled by the threat of a shift in available inventory. People will continue to buy more products online, he says, and Gilt Groupe will take up a healthy piece of that spending pie. Gilt Groupe will not sell its data about these customers' shopping behavior, but it will model it, Ryan says. That allows Gilt to match its content to its shoppers. For example, the company sends out 2,000 different versions of its daily newsletter to its more than 3 million members, Ryan says, based on their preferences. Its data modeling also provides Gilt with a kind of Holy Grail in advertising: quantitative data on the spending patterns of loyal, wealthy, nearly recession-proof consumers. Other department stores looking to reach out to buyers can't access these big-spending customers the same way, Ryan says. "A Saks or a Macy's can't do this because they don't have a membership-only model. The only people who can do this are flash sales types and Facebook."