As best as I can tell, all it would take is for the men who run our power and water to not go to work, and society would come to a screeching halt. How many is that? One out of 100? One out of a thousand? One out of a 100,000?
If cops or fireman or doctors didn't go to work, some ways society would get better and in some ways worse, but it would not collapse. But with no water or power society would be close to collapsing in an hour.
When I was a newspaper editor I interviewed a man who was the head of a state-of-the-art waste treatment plant. I think perhaps ten guys worked there. Imagine if they didn't go to work and that facility didn't process all the sewage. My God, it would be a horror. Chaos and horror.
If you think about it, it is amazing how fragile society is.