It happened with Grand Theft Auto IV, and now it's happened with Metallica's "Death Magnetic". Yes, it has been leaked. I'm not that surprised, to be honest, it was going to be online at one point or another. Whether before, or after it's release, was just another story.
Personally, I'm not going to be downloading it. I want to buy it, if I don't like it, I'll probably just resell it.
I ain't giving any links, go to any warez site or torrent site and you're bound to find it. Kind of annoying, to be honest. People pay more for convenience, I know from experience (and when I mean "pay more" I don't mean in money).