I guided my children's reading, television, and movie consumption until each was about eleven, and then I let them go. They were exposed to the best, and at some point, one must trust that one has provided enough exposure for a child to make his or her own judgements. That was the way my brother and I were raised, and we both felt it worked out very well for us. My children have read all sorts of books they chose for themselves, some good, some bad, and some in between, and they have figured out for themselves what is worth reading. My youngest is 21 now, so perhaps the evidence is not all in, but since we all recommend books to one another frequently and satisfactorily, I think that things have worked out well in my family, too. However, having said that, I should also say that every set of parents is different, as is every child, and there is no right or wrong in this matter. The fact that your parents read the back of every book is a good thing, showing that they care about you and are interested in what you are reading.
I generally agree with post number three, though it is difficult for me sometimes. I think it depends on the individual parent. Some parents think it very important to impose (perhaps too strong of a word) a certain set of values on their children. To this end, they try to control what information their children have access to. I understand where they are coming from, but I guess the values I want to instill are more related to tolerance for different viewpoints and intellectual curiosity than to any particular values system. Obviously, there is no place for some adult literature with very young children, but as a parent, I choose to be pretty open about what my kids can read. I will say that it's important to discuss whatever they're reading with them, because I think that's a great way to really digest what they're reading. Like I said, though, I can understand those parents who want to be more controlling. It's a difficult line to walk sometimes.
I don't think monitoring the books a young adult reads is any different than monitoring the TV shows they watch or the music they listen to. Parents are responsible for their children and they want to protect them. Good parents monitor many aspects of their children's lives (especially when those children are gaining some independence as young adults). There are many books that might not be appropriate. There are books that might share ideas that go against a family's value system. This isn't to say that the young adult shouldn't read those books, but a parent might want to discuss the information with them and help them understand certain aspects of the new information. I know my parents certainly monitored what I was reading. They rarely asked me not to read something but there was a lot of discussion about certain books that they found controversial.
Personally, I don't think so. I don't see what my child is going to read that is going to be so horrible and traumatic. I remember when I was about 10 and my parents were unhappy with a book of theirs that I wanted to read. I'm not sure if they disapproved of me reading the violent parts of of the very few and non-explicit sexual parts. One way or the other, I don't think either had much impact on me.
I can't police everything that happens in my kids' lives and I need to give them some space. Besides, unless I'm going to read every line of every book they read, how am I going to "protect" them from everything "bad" that could be in a book?
A good parent should at least be aware of what his/her child is reading, but a good parent will also allow their child enough independence to develop their own reading tastes. The act of reading is certainly more important than what is being read, and with all of the other electronic distractions that compete with reading these days, parents should not try to discourage their kids from enjoying books.
Being able to have a conversation about the books you are reading with your family seems like a good thing. Maybe direct oversight/vetting isn't necessary, but a parent's knowledge of what a child/teen is reading can let the parent ask how the reading is going. This can help the parent to anticipate where the reader's interests are headed or simply create opportunities for conversation.
I think that your parents are looking out for you. Whenever I assign a book report I have my students bring in a permission slip. Parents should know what their children are reading, just like they should know what you are watching on television.