You can, for instance, purchase a TV series in HD and watch it on your Mac or Apple TV...but you can't purchase an HD movie at all, and you can only rent them on an Apple TV, not a Mac. Why? What's different about an HD TV series and an HD movie?

From my chair at least, nothing. I know, behind the scenes, they're controlled by two very different entities, but as a consumer, such things shouldn't matter. When I want to purchase HD content, I want to be able to use it on whatever device I wish, and transfer it easily between all such devices I own. The current model is just completely confusing, and makes no sense.

Of video and piracy

It really makes no sense when you consider that the video industry is taking these protective steps against those who are probably least likely to steal their content--consumers who have decided to purchase through the iTunes Store. We've made a conscious decision to buy our audio and video through the iTunes Store, and yet the video industry treats us as though we're all pirates foaming at the mouth, ready to upload our freshly-purchased content to every pirate server in the known universe.

One way to really alienate your customers is to treat them all like thieves and criminals. (I'm not sure the music industry has fully learned this lesson either, given some of the RIAA's tactics...but at least record companies are making strides on DRM.)