Common sense and DRM
Sensible words on DRM from cryptographers (who ought to know a thing or two about it): "Anyone designing content protection should design for failure and if it fails update it"
On a related note, and stating the obvious once again: the raison d'etre of DRM is to protect the music industry from losses through music piracy. So why is it that, to purchasers of music, DRM is most evident from the way it stops you doing things you've always done with music (moving it from place to place, playing it where you like, limiting number of plays), rather than stopping you from participating in mass piracy?