Managed Copy
No, it's not some .NET backup tool... Managed Copy is a feature of next generation optical discs (HD DVD, Blu-Ray).
Managed Copy is the ability to copy the content of a disc onto a hard disk for playing on a computer network. Permission to copy stuff off the disc is something I didn't expect at all from the next generation formats.
It's a point of contention between the two competing standards, since HD DVD has mandated that all discs must support Managed Copy, while with Blu-Ray it's optional.
To me, this is the deciding vote between the two.
Not that it's going to matter in the long run - two competing standards, each with studios and equipment manufacturers behind them, means that eventually we'll all need players that support both formats.