I think TV has changed a lot since I was younger, it's certainly more violent and contains more sex, nudity, and all that. Having said that I think that there is a lot of good television out there, even quite a bit that could be considered "educational." I don't know if TV can be blamed entirely for our desensitization to violence, sex, and drugs. In a capitalist society, the consumer has the choice of what he/she wants to consume, nobody is forcing anything upon anyone. Having said that, it is getting harder and harder to avoid these things in the media. The main concern with this is of course, children. Kids don't have the maturity and wherewithal to make those choices.
I think I spend too much time watching TV, I use it as a way to kill time. Growing up, my mom always limited the amount of time we watched TV. After a couple of hours she would come shut it off and tell us to go read or exercise. It always angered me, especially if I was in the middle of a show. But it retrospect I can see that she was looking out for our well-being. I don't have kids, but if I did I know that I would put parental controls on our TV and internet. This is a tricky area because when something becomes "taboo" or "off-limits," it becomes all the more appealing to adolescents. Their curiosity gets the better of them. So I don't know if there is a clear-cut solution to the problem of kids being exposed to sex and violence in the media.