Flash sales are an amazing phenomenon.Companies like Fab.com have been conducting these curated sales, with each item available for only a very limited time, to great success (Fab recently raised $40 million in new investment, and will generate over $100 million this year). And they are not alone: there are literally dozens of flash sale sites, ranging in specialties on sporting goods ( The Clymb ), furnishings ( Joss & Main , etc.), and every vertical under the sun. For the consumer, quite the win. Or is it? The interesting evolution of flash sale sites start with the same premise. Take, for instance, the come-hither for one of the flash sale granddaddies, Gilt Groupe : "Join Gilt to find the best brands at up to 60% off". Each of these sites promise unheard of savings on amazing brands, all for extremely limited times. And in the early days of their sites, it is so: many run staggeringly low prices for brands. Why and how? Simple: acquisition marketing. These sites