I was around at the time, and there were half a dozen other platforms that took centre stage once Napster closed its doors. Morpheus, KaZaA and eMule were my main ones. Free music was as available as it ever was, so in that sense all Metallica did was lose fans and annoy everyone.

The basic concept is still around today in the form of Soulseek, which is where I get 99% of my pirated music from (such as Metallica's). BitTorrent mostly supplanted these kinds of programs, though.