I know it wouldn't be useful for security, but what I'm thinking is being polite. I like posting quizzes for the world to see - so public - but I know some of my friends don't like them. So I'd setup an inverse filter to keep my quizzes off their pages. The reverse, having to put everyone on my friends list to show them the quizzes, is completely unappealing to me.
Just a random thought before bed.