@ Amos2: CRM: use the available recources. One of your pax could be a another pilot or engineer. A recent incident in a South European country springs to mind where one of the pax told cabin crew during taxi that they just hit another aircraft with their wingtip. Turns out the pax was an engineer. Turns out he was right. Turns out the crew was not aware.
I wouldn`t go as far as making a PA though in every abnormal or emergency. Most likely the info from “the great unwashed down the back” will come to you without a PA. Some of it might be valueable.