Originally posted by Glass Arm Shattering:
Of course, but I had no problems hiding the pornos from my parents when I was kid. Why can't a world-famous rock band lock away their master tapes properly? Something just doesn't compute 
Chances are it wasn't leaked by the studio, probably some music journalist who got an advanced review copy. And for a release by an established band, they send out thousands. magazines, daily papers, college papers, blogs, etc.
Leaks that come long before the scheduled release (the last broken social scene and the upcoming tv on the radio come to mind) are more likely to be someone involved in the creation of the record. Probably an intern who made a copy for himself, had it borrowed by a friend who made copies for his friends, etc.
