This is a good point, 'how much’ is an important question.

But then, it seems society sometimes make the decision to take somethings off the table entirely.

I look at the accident at Fukushima, and earlier (when I was small child) Chernobyl and I can't help wondering whether some risks aren't worth taking when there are alternatives available.

I'm sure risk analysis was taken seriously in Japan. Often we miss things, and the people answering 'how much', quite frankly get it wrong.