The validity of the recent BI study that claimed pirates buy more music is being questioned by Maura @ Idolator and cohort Eric Harvey, and rightly so. The soon to close Dotshop, a connoisseur's internet shop of sorts, may well be in the right when they claim that they are victims of illegal filesharing.
Thing is, though, I have in fact bought more music because of the availability of free music on the internet, from the simple cause and effect that more music has been more easily available for me to hear before I buy the damn thing. Now while I do not claim to be a typical consumer, whose to say I'm only one in a million? Furthermore, most music fans I know prefer the physical LP or CD to mp3/FLAC/what have you, but this is a banana skin on par with the Nixon "qoute"; I don't know many people and other people may not give a toss or two about what format they listen to, much less how they obtain it. Those people do in fact hurt sales.
Thankfully, the likes of Spotify and their increasing libraries of music may make illegal filesharing for the sake of "getting a taste" increasingly redundant. They are the listening posts of the future, me thinks.