Coruscation

Custora, which also works with sites like Etsy and Revolve Clothing, creates similar online dashboards. But its specialty is identifying the most valuable customer segments and using algorithms to forecast their potential spending over time. Right now, for example, only 15 percent of Fab.com purchasers shop with the company's iPad app. But a Custora forecast estimated that, over the next two years, a typical iPad customer would spend twice as much as a typical Web customer and that the iPad cohort would generate more than 25 percent of Fab.com's revenue.

In an era of online behavioral tracking, Fab.com has been more transparent than some other sites about a lot of its customer surveillance, data collection and analysis. Mr. Goldberg writes regularly about the company's social marketing practices and metrics on his blog. Likewise, when Fab.com was seeking seed money last year, Mr. Goldberg gave several venture capital firms passwords to the RJMetrics' dashboard so they could see the company's revenue and customer trends for themselves.

"V.C.'s could see it every day," he says. "They could come back and say, 'How did Fab do today?' "

Last December, Fab raised $40 million from Andreessen Horowitz, Menlo Ventures, First Round Capital and several other sources, including the actor Ashton Kutcher. Mr. Goldberg, meanwhile, is now an investor in and a board member at RJMetrics.

THIS month, the site even re-engineered its look -- to Fab 3.0 (post Fabulis)-- to capitalize on recent data indicating that users who had checked out the site's crowd-sourcing feature were more likely to make purchases than those who had not. Among other updates, the site now gives more prominence to a live feed featuring the products that members have just bought or liked.