So I've been following all the Engadget and Gizmodo posts about the rumored Argo and Zune. One of the things that jumped out at me was this Engadget article that talked about the possibility that Microsoft would be allowing people to download whatever music they've purchased in iTunes for free — but that “Microsoft will still have to pay the rights-holders for the songs”. (Note that this was later refuted here on Gizmodo)
Whether or not it's true, I do think this points out a serious flaw with having multiple formats of proprietary DRM: you've paid for the song in one, but you can't get it in the others — even though you paid for the license to the song! I guess what you're paying for when you pay $0.99 in iTMS or any of the other content providers is a license to that song, using that service. Makes the “buy this song” links seem kind of like false advertising.
I've said before I have no problem with the concept of DRM, so long as it's done right; the current ways, however, aren't. This is one aspect that I think a unified approach that would work on multiple platforms would be a boon to consumers. I'm having this problem currently with the music that I've bought from iTMS since I sold my iPod in favor of a Toshiba Gigabeat S60. So far, I'm leaning towards (and have been checking out) for two months MTV's URGE music store subscriptions – so I can just re-download what music I had previously encountered in iTMS.