My TV does motion smoothing? Really? Apparently, yes, it does. I had no idea.
Actually, as it turns out after I checked, my TV doesn't. It's too old, I guess. On the other hand, it is set by default to "Vivid" mode, another hellish abomination that I'm supposed to turn off. "Cinema" mode is preferred by the cognoscenti. You learn something new every day.
Anyway, the linked column is from Scott Tobias, and he recommends this post from Stu Maschwitz if you really want to understand what's going on with your shiny new high-def TV. It was pretty interesting! Personally, though, I'd be happy if I could just get my TV to consistently use the correct aspect ratio all the time — or, in a pinch, at least have enough manual settings that I could always choose one that works. But it doesn't seem to. It's too old, I guess.