First, a preface…I’m as in favor of widescreen and letterboxed movies as I am of anything. In fact, it’s about the only subject on which I’m completely willing to declare anyone who doesn’t share my viewpoint completely and unquestionably wrong. But what I can’t figure out (possibly because I have a very poor grasp of numbers and spacial relations) is why you would shoot something in 2.35:1 or 1.85:1 if it were never going to appear anywhere but TV. I understand that it means an image with a greater ratio of width to height- duh- but why is this worth using only half of the available screen space? Granted there is likely to be more action on horizontal plane than a vertical one, which might mean a less action-packed top and bottom, but so what? I don’t see why a perfectly good composition can’t be made using a standard TV aspect ratio. So am I missing something obvious that commercial, music video and ER directors have figured out? Or is the recent trend towards letterboxing on TV just an attempt to dupe the many morons who know only that letterboxed=cinematic=automatically several notches better than normal TV format?
Well, one thought is that the new-fangled higher definition television sets are built with more cinematic aspect ratios.
I know that when I was in Jersey (the island, not the state) this past summer, the TV in the hotel room had a (?) 16x9 aspect ratio. Some of the channels had a “wide-screen” mode, so I watched a couple of fairly mediocre shows in glorious widescreen television.
Here’s a theory for music videos at least. A lot of video directors are really just wanna-be movie directors. So they’re really using the videos as high-priced audition material, and to further that goal they have to prove they can handle the wide screen. Brett Ratner is one of these guys – he moved from rap music videos to directing Rush Hour. On the other side, some movie directors like to screw around and direct videos on the side. But of course a big-time movie director would never work in TV (the horrors!) So they use widescreen ratios because it’s what they’re used to and it doesn’t look like TV. Plus it’s just the current fad, so everyone’s doing it. Commercials are in precisely the same situation as well.
ER is doing it just because they’ve run out of creative ideas and have to resort to stunts to get viewers.
Not necessarily. Remember, the networks are phasing in HDTV broadcasts now, on a show-by-show basis. NBC may be broadcasting ER both in regular analog and HDTV formats, and composing the whole thing for 16x9. If you’re going to broadcast a show in two formats, why not compose it during taping to accommodate the better of the two formats even if fewer people have access to it?
Plus, there’s something to the supposition in the OP–using a widescreen ratio gives you a lot more freedom in composition. You can afford to do more in the horizontal frame, in which people expect the action to occur, than the vertical.
Which commercials are wide-screen? I have a TiVo 
so rarely see commercials at all anymore, but I’d like to see who’s using wide-screen just to see it.
If you shoot something in widescreen, it protects you from obsolescence. In 10 years, most everyone will have a wide screen TV, and these old 4:3 broadcasts will look archaic.
BTW, Stanley Kubrick shot most of his movies in 4:3 format. A vertical mask on the top and bottom of the frame is used to convert his movies to 16:9. So there’s nothing stopping you from creating great movies in whatever aspect ratio you choose.