Not only "monitored closely", but also strictly limited, from day one.
First because, as you so accurately point out, broadcast television is rife with advertising. Even when the content of the shows is unobjectionable, the advertising promotes materialism, greed, the fast-food culture, bad health habits, slangy language, and pert or discourteous behaviour.
Second because, as you also note, the optic nerve is a high-bandwidth neural highway directly into the brain. All those fast cuts, zooms, and flashing lights DO affect brain chemistry -- as anyone who has dealt with epilepsy can tell you without reading any research papers. And if you do read the research papers, they confirm it.
Third because, the choice of "no television" is a GOOD choice. Alternatives like playing in the park, dress-up and make-believe, climbing trees, helping with dinner and baking, roller skating on the sidewalk, bike-riding, playing with dolls, colouring, dancing, making music -- ALL are diminished by the amount of time that is spent watching television. Paediatricians are crying out that we face an epidemic of juvenile obesity and poor fitness; teachers are bemoaning the lack of imagination shown in original work. And both of them will tell you that children raised with minimal TV are relatively immune to both syndromes.
On the flip side, if you've just gotten home from 8 hours of work plus a commute, and picked up your child at the daycare, and come into a cold dark house where you need to START getting dinner on the table and are doing the daily clean-up as you go, there's no question that having an alternative to entertain your child while you prepare supper is a godsend. I kept a tape of a few favourite low-key shows sans advertisments -- things like the Ringo Starr "Island of Sodor" shows, "Thomas Tugboat", and even a couple of Barney episodes; and played ONE for Anne on returning to the house to help us transitioning. Later, when Rachel was a toddler, I had a neighbour girl come in for half an hour before supper to fold diapers and play with the children. When I say "Brandy is better than television", I'm not expressing an incipient alcoholism, I'm expressing how much healthier it is to have a living breathing human being for companionship than to rely on broadcast companionship.
I don't see any reason to ban TV completely. But some good groundrules would be, limit TV to some small number of shows a day; pick the shows ahead of time; and intentionally turn the TV on just before one starts and off as soon as it ends. That way it won't become your children's default alternative to having a life (which I define as human companions, tree-climbing, active play, household chores, and imaginative play).
You also won't have to go through the transition I go through every two weeks when my part-time children arrive. 11 days out of 14, they have the TV on for nearly all their at-home waking hours. Then they arrive here, where the TV is occasionally on for a special on Saturday evening, but we're usually to busy. They are like bored little stumps for the first two hours"
"Auntie, can we watch TV?"
"Nope. Why don't you go see what Anne and Rachel are doing. Or, you could fill a bucket with apples for me, or you could play with the dress-up"
"I don' wanna."
10 minutes pass.
"Auntie, I'm bored. Can we watch TV?"
"Nope. There's lego on the toy shelf. Or you can take a hose and spray down the windows outside. Or I think the girls are making up a play -- maybe you can be the Prince.
"I don' wanna."
10 minutes pass.
"Auntie, I'm bored. Can we watch TV?..."
(repeat 5 or 6 times) ... then ...
Gradually, I realize 30 minutes have passed with no interruptions. Suddenly, one or both part-time children burst into the room.
"Auntie!We-made-up-a-play-and-we-want-you-to-watch-it-and-can-we-have-some- paper-to-make-a-backdrop-but-first-we-want-to-climb-the-apple-tree-so-can- we-have-a-bucket-and-I-need-my-helmet-cause-Anne-said-I-can-ride-her-bike- where-are-the-crayons?"
And from then on typically no-one mentions TV again.
The teachers at the girls' school tell me that they can tell, just from the way children interact and play, and from the content of their creative work, which children are reared in the typical way with the TV on as background entertainment, and which ones are reared with no or minimal TV.
In later school years, though, many Civics assignments involve watching TV, and English teachers may try to make their assignments "relevant" by referring to popular TV programmes. For children like mine, who have never seen an episode of "Survivor" or "American Idol", that could be a bit alienating. Fortunately (and perhaps relatedly) however, my children are also quite capable of explaining lucidly to a teacher that, while they don't know anything about "Lost", they do know the entire libretto of Nutcracker and most of Giselle, and would happily translate the assignment to a more valuable idiom than TV. I've never had a teacher insist that the girls do their work around TV instead of classical ballet or literature (and if they did so insist, they'd probably lose the argument in the end. They're educating MY children, after all, and I'm the one ultimately responsible for my children's schooling. Most teachers seem to understand that.)
