How open should families be when it comes to sex?

All families differ when it comes to the topic and discussion of sex. Openness about the topic can benefit parent-child relationships more then most know. As a parent I appreciate the fact that my children feel able to come to me with questions freely pertaining to the "forbidden topic" in other families. There are no barriers, and gives me a safer feeling about what my kids are doing. I know what my kids have learned about sex. This helps me to advise them in the best way possible.