"Keeping secrets" might be known technology, but so is "convincing the public to accept risks." (E.g., they accept automobile fatality rates.)

Has public opinion on auto safety changed over the years? We certainly don't require footmen to wave flags in front of cars anymore, but I doubt that ever reflected general concern.

What are good examples of big attempts to change public beliefs about risks or actions that might reflect beliefs about risks?

US government campaigns about drunk driving and smoking spring to mind. My impression is that they affected actions but not beliefs about risk. I'm not sure whether they linked belief to action better, or whether they changed action for other reasons (eg, coolness).