So you've got HD networks.
On these HD networks, sometimes the content is still SD.
Sometimes, they'll just have the bars on the side of the screen, often displaying the logo of the network on each bar. If you have to, by all means, do this.
Sometimes, they'll stretch the image uniformly to fit the entire screen. Guh...
And sometimes, they'll stretch only the edges. So the stuff at the center is rightly proportioned, but the stuff on the edges is distorted like crazy. And when things pan in and out of the center of the screen, you'll see them stretch and distort on the fly. Who in the world thought this was a good idea? It's the most annoying, must distracting, most... vomit-inducing method of dealing with SD content on HD networks that I can imagine. Seriously... just show the bars.