agree with hmc's message - I don't think the chance watching of an undesirable TV progamme does untold damage as long as the home environment is OK. TV watching is a valuable wind down and part of a mix of activities in our household too.
My children don't have a TV in their bedroom but I have no strong feelings anti - there are so many ways of limiting viewing (pull out a cable, fiddle with the channels, lock the bedroom door etc). OK, your child may see something unspervised but unless you can say, hand on heart that you are always in the same room with tham when they watch any TV, then what's the difference? What's to stop you regularly checking up on them in the bedroom?
We have just got a TV in our bedroom and it's great. My 4 year old can watch things appropraite for his age - Thomas the Tank - while my 9 year old can watch something like Fort Boyard.
With a big age gap between children, having 2 TVs is a big plus.
Incidently, I am really happy for my 4 year old to watch toy ads - he knows he won't get the toys he sees usually. In the same vein we often go to toy shops to view the toys but not to buy them. Seeing toys in a shop or in theads holds his interest and fire his imagination. We talk about them later, and he describes the toys to me and what he likes about them.
He was looking at a box this morning and pointed to a word on it and said 'matchbox' - he'd learned the look of the word from a TV ad and knew he was picking out the word. Now that is something for him. He likes books but is not yet at the stage of wanting to read or recognising words from the alphabet (we have done simple worksheets but he's not that into them). If a toy ad can inspire him to search for words then that's fine with me!