Giz Explains: Why HD Video Downloads Aren't Very High Def

Yesterday Apple introduced HD TV downloads » 9/10/08 2:20pm 9/10/08 2:20pm to the iTunes store, meaning you can watch Peter be emo on Heroes at a crispy 720p resolution. That's a higher resolution than DVD, and technically, yup, that's HD. There's a catch though. Like every other video download service touting HD videos, it's all actually lower…