1 - I think media expands one's knowledge and it often can do more good than bad, but it also can be used against the people watching it - TV can be often political and misrepresent some events shown on it.
2 - No, I think as long as there are limits to watching it, it does no harm. Sure, you shouldn't be spending all your days at the TV because it's just unhealthy.
3 - There is always equally good and bad things in everything. There is a lot of rubbish on TV, but then there are many wonderful TV shows that you can watch to learn something - documentaries about nature, musicians, movies and history. A lot of Discovery shows are really great.