It's been a while since I've read anything about DRM, but everytime I do it angers me.  For those who might not know, every song or video you buy and download from the internet (i.e. from iTunes) it has DRM that prevent you from enjoying that content in as many situation as you could with a CD or DVD.  The same will be true HD-DVD and Blu-ray.  But I don't think I can articulate the movie industies desire for DRM better than Ken Fisher's article on Ars Technica:

Access control technologies such as DRM create "scarcity" where there is immeasurable abundance, that is, in a world of digital reproduction. The early years saw tech such as CSS tapped to prevent the copying of DVDs, but DRM has become much more than that. It's now a behavioral modification scheme that permits this, prohibits that, monitors you, and auto-expires when. Oh, and sometimes you can to watch a video or listen to some music.

The basic point is that access control technologies are becoming more and more refined. To create new, desirable product markets (e.g., movies for portable digital devices), the studios have turned to DRM (and the law) to create the scarcity (illegality of ripping DVDs) needed to both create the need for it and sustain it. Rather than admit that this is what they're doing, they trot out bogus studies claiming that this is all caused by piracy. It's the classic nannying scheme: "Because some of you can't be trusted, everyone has to be treated this way." But everybody knows that this nanny is in it for her own interests.

Like all lies, there comes a point when the gig is up; the ruse is busted. For the movie studios, it's the moment they have to admit that it's not the piracy that worries them, but business models which don't squeeze every last cent out of customers.

In a nutshell: DRM's sole purpose is to maximize revenues by minimizing your rights so that they can sell them back to you.

Be sure to read the full story, Privately, Hollywood adminst DRM isn't about piracy.