I watched a lot of TV as a kid, and I had a small black-and-white TV in my room starting at age 13 and really enjoyed it. It didn't hurt me, but frankly I would like my son to watch less TV than I did, and not to have a TV in his room at all. (To set a good example, my wife and I do not have a TV in our bedroom, and are happier than when we had one.)
I was a kid in the days before cable, internet, and DVD/videotape, we had a fairly limited selection of over-the-air TV stations, so it was harder to watch TV as many hours as are available now. And especially looking at "kid's TV" these days, it sure seems dumber and more commercial than I remember it. Like the shows are slapped together only as a pretext to show them as many ads for junk food and plastic toys as possible.
Despite hoping my son watches as little TV as possible, I don't want it to be so little that (a) he loses touch entirely with popular culture, or (b) misses out on some legitimately good stuff that can be found on TV (albeit the rare needle in a haystack of crap), or (c) it becomes "forbidden fruit" and the main way for him to rebel is to watch as much mindless TV as he can.
I think new technology may help: DVDs, internet video, and Tivo allow us to pick what we watch rather than settling for whatever rubbish is on, to skip commercials (or not have them at all), and to "time shift" (e.g., "TV only on weekends" or "only after homework is done" doesn't have to mean missing favorite shows, as it did when I was young).
So the bottom line is that I'm leaning toward never allowing him to have his own TV. Though once he's a teenager, if he's a responsible kid and a good student, it would probably be hypocritical for me to deny him as long as he was spending enough time being physical, reading, socializing, and attending to his academics. But I hope that in his younger years, I can limit the TV and maybe he'll never get hooked enough to even want a TV in his room.
As an aside, I feel like I have to say that the above discussion is geared toward older kids and teenagers. For young kids and toddlers, I think TV should be avoided as long as possible. Some references: