Most people don't buy movies on their computer. It's more logical to buy a DVD set, which plays on both TV and computers, than it is to buy a digital movie that can't be moved back easily. Computers don't offer much of a movie-watching advantage, so the computer-movie market is floundering.<p>The iPhone lets me buy movies on the fly, which gives me a great convenience. But it's small. The iPad, on the other hand, lets me buy from anywhere, but it's large enough to make movies enjoyable. If I'm about to get on an 8-hour flight, maybe I buy a book and rent a movie. The fact that I can pay a small amount of money, get something to watch on the plane, and never have to worry with physical packaging, that's nice.<p>Certainly that encroaches on Apple TV. But Apple TV is a bastard son anyway.