A quickie before I go to bed, I may or may not write more on this topic later.
As a society, we try to make children safer by educating them about the dangers they may face. Two major problems with this are that even adults don't understand the problems or the dangers. Children are more likely to be molested by people they know and trust, but the emphasis is placed on "stranger danger." In our attempts to simplify things so that children understand them, we leave out important details that might help them generalize concepts to a variety of situations. Children with developmental disabilities in particular often have trouble generalizing concepts--if it doesn't fit exactly with the examples they know, they may not recognize the same type of situation if some details are changed.
Parents might fear that their children will be abused at day care--but by the staff. What if the real danger is other children? http://sweetperdition.wordpress.com/2008/04/21/no-words/
I was 23 years old and had been living away from my parents for two years before I realized that my father was an alcoholic. There were countless examples of alcoholism that I was shown as a child and a teenager--at school, girl scouts, and cultural examples on television and in books. My father wasn't like the examples that I saw, but he still abused alcohol, and it affected him, his marriage, his family, and his other relationships.