Ideeli, one of the popular flash sale sites, sells designer duds at deep discounts for limited-time periods.
NEW YORK (CNNMoney) -- Online retailers that offer luxury items at deep discounts have created a billion-dollar industry in a flash.
In 2007, as the economy tanked and the demand for luxury clothing and accessories dove south with it, a new market emerged online. An online retailer called Gilt Groupe started selling high-end merchandise on its members-only site and ignited a fuse that has exploded into one of the fastest growing trends online: flash sales.



