Having a thief (sorry, 'copyright infringer') take your software rather than pay for it may eventually provide some word-of-mouth advertising, but they're likely to tell other pirates and repeat the cycle of revenue loss rather than become vocal advocates for a purchase.
Outside of edge-cases like Microsoft (whose Windows dominance was arguably helped by piracy) it seems that 'piracy is good advertising' is a fallacy used by pirates to make themselves feel better about denying income to people they otherwise like.
Can you name three small software producers whose revenue grew stronger as a result of piracy?