ArsTechnica reports that DisplayPort uses DPCP (the DisplayPort version of the evil HDCP) on iTunes purchased content. So if you want to watch that movie you bought off the iTunes store on an external display such as a projector or your 30 inch cinema display, you may not be able to, if you have any non-conforming display connected. Instead you see a dialogue proclaiming:
This movie cannot be played because a display that is not authorized to play protected movies is connected. Try disconnecting any displays that are not HDCP authorized
So one has to think this is likely to increase the probability that rather than downloading it from iTunes people will download the pirated torrent instead.