Consider this.. When limiting someone, you are interrupting whatever it is that they are doing which makes them think about it that much more. By not allowing something at all (Within reason of course.. like games and TV) you are depriving the child of that experience. If it's something that they are interested in, or want to explore or play with you are better off letting it run it's course. Otherwise when they feel they are free to do as they please, they go crazy. For example.. a child who is told that he can have no cookies at all, ends up just wanting cookies. It becomes almost an obsession. The child goes to Grandma's house and gobbles them down until he gets a belly ache. While a child that is told they can have as many as they like are more likely to control themselves and make a good decision about how many they have. They know that they can come back later, or tomorrow and have another.
I am not ashamed to admit that we let our children watch television. We set no time limits and we do not choose what our children watch (within reason, of course). In letting our children choose what they want to watch, when, and for how long, they get to feel a sense of control. Not surprisingly to me, they are very naturally responsible about this. They often choose educational material. They love national geographic, Disney nature, and just about anything on PBS. Of course there are times when they just want to watch a cartoon because it looks fun and colorful, and that's fine with me.
When someone asks me "Why are you letting them watch this? It's not educational..." I don't see any reason to restrict their TV watching to educational only. While educational shows and movies are very helpful, there should also be time for them to just be a kid and watch television for recreational purposes.
My children do not watch TV all day long. By no means, but if one day that's all they wanted to do, I would be okay with that.. and if one day they choose not to watch it at all, then of course I am okay with that too. I would however encourage other activity if they were being couch potatoes all day. My children never choose that though, so it hasn't been a problem.