> Interestingly, at least one poster acknowledged that she had in fact downloaded the music in question, suggesting that the scammers had collected real file-sharing data and connected it to peoples' real names and physical addresses. It's unclear how they managed to obtain the information.

I'm going to take a stab here and say that they picked a popular piece of music and sent out letters about those. A decent portion of the population will have downloaded this stuff, just by coincidence.