One study found that users of pirated software sufficiently influenced by word-of-mouth communication eighty percent of the software's prospects to buy the legal product and another described several scenarios in which piracy can help increase the sales of legal products. The pirated product functions as a free sample that the innovator does not have to fund.
The rest of Jerry Kirkpatrick's article, "The Market Function of Piracy," is here at the Ludwig von Mises Institute.