When most people think about the effect of counterfeits on legitimate brands–and when brands themselves litigate against counterfeiters–they focus on the “business stealing” effect: Every fake Prada handbag represents a lost sale for Prada. But a dirty little secret is that Prada rip-offs can also function as free advertising for real Prada handbags–partly by signaling the brand’s popularity, but, less obviously, by creating what MIT marketing professor Renee Richardson Gosline has described as a “gateway” product. For her doctoral thesis, Gosline immersed herself in the counterfeit “purse parties” of upper-middle-class moms. She found that her subjects formed attachments to their phony Vuittons and came to crave the real thing when, inevitably, they found the stitches falling apart on their cheap knockoffs. Within a couple of years, more than half of the women–many of whom had never fancied themselves consumers of $1,300 purses–abandoned their counterfeits for authentic items.