Apple does this with iTunes/MobileMe, and any cloud storage player is aiming for the same network effect.

The cloud storage play is huge for Apple... first they sell you the video, then they sell you the space to store the video, but it doesn't actually take them anymore hard drive space.

And as the media gets bigger and bigger (HD today, who knows tomorrow), Apple sells you more and more storage "space" and their costs only go up marginally.

It's the stuff billion dollar business plans are made of.