The concept of the ever-replenishing closet was born, and Ms. Hyman and her eponymous co-founder set out to make a wider selection of couture dresses available to women who are on a budget but still looking to dress up for a night out. The online rental service offering choices from a range of designers, which now include Vera Wang, Nicole Miller, Diane von Furstenberg and Escada. The dresses are available for a fraction of the retail price, with most ranging from $50 to $200 per four-day rental. It's not chump change, but women will happily pay up for high fashion and variety, and they have more than a million active users, according to TechCrunch--we don't even want to attempt to multiply those numbers.

Let's just say the revenue looks substantial, and it's no surprise the co-founders raised more than $30 million fromHighland Capital, Bain Capital and Kleiner Perkins, in order to expand its inventory and distribution.

"Over 90 percent of our renters have reported that they have purchased something from the brand they rented, post rental," Hyman told Inc.com, suggesting lead generation could be another revenue source in the future. "We are effectively grooming the next generation of women for high fashion."

Rent the Runway expanded to jewelry and handbags, and the two-year old company is up to 45 employees, mostly women.