I understand why it exists, but from a user's standpoint I think it's one of the most irritating and counterproductive things known to man.
For example, I wanted to watch an episode of The Simpsons on my wife's MBP, which was purchased in the US, otherwise known as Region 1 in the DVD industry. The Simpsons box set, however, was purchased in Germany (aka Region 2).
I wasn't about to start eating into her allotted region-switches on the internal DVD player and VLC couldn't read the DVD for some reason. So I went on BitTorrent and downloaded the episode in about ten minutes.
A common example of a legitimate, authorized user who was frustrated and thwarted by DRM and instead turned to back-alley channels as a solution.
I've made one music purchase from the iTunes store to avoid the very same situation. iTunes Plus is a step in the right direction, but 256kbps is still too lossy for my tastes.
As someone above mentioned, DRM doesn't stop piracy (though it might delay it a day or two), it only nags and impedes legitimate users.
