4. Beyoncé - 4 Deluxe Edition
This is a slightly left-field one. Not, of course, because it's Beyoncé - she is a huge star, and she was bound to be on the list - but because it's 2011's 4, rather than 2013's self-titled, that has been downloaded more frequently. Given that illegal downloading has only grown in the years since 4, you'd have suspected her later album would have been pirated more!