Older DVI monitors withoutcontent protection will get nothing but a blank screen when playing protected content (read: any commercial Blu-ray or HD DVD disc released).
Technology withoutcontent support hit us on two fronts -- iTunes 8.1.1 made HD rentals possible, but we're still waiting on content, and then ESPN touted its 1080p production facilities that can pump out content that won't fit into any broadcast or media.