unless many of those people would have bought anything (more importantly, the same thing) if there was no filesharing, that's hardly an issue.
I haven't heard x or y famous Metallica album (I know all you Americans have been familiar with them since you were 10 years old...but not everyone has). It will never be played on the radio (which, in any case, I don't listen to), nor on TV (just the occasional 'single'). Unwilling to pillage them thar albums in 56k (downloading) or broadband (streaming)-friendly ways, since they be such scallywags, I can assure you that I will never send any money in their direction. ...if I was to download something of theirs, it wouldn't be the downloading that does any harm to their profits. The downloading would do little more than facilitate my interest (kinda like Dragon's Den--it gives them the opportunity to be heard by someone who might or not might want to spend money, who certainly isn't spending it there while it's unheard). The worst case scenario where downloading is involved, is where I like a song, keep the song, enjoy it, and never give them any money.
As a bitter angry spiteful hateful person, I can appreciate how Metallica would feel about someone being happy thanks to you, but giving you nothing in return, but it's not clear that I'd really feel that much schadenfreude, that much satisfaction to know someone has been prevented from enjoying something free/unexpendable that I want reward for.