Yes strange men can be scary too, especially if they have to come in the house like to check the furnace, my cat will hiss then hide.
Its seems like most cats are afraid of the vacuum, are girl cats more scaredy cats than the big brave boy cats I wonder?

That story of Marius jumping straight up in the air reminded me of the times when my cat sees or senses something that I don't and gets all fluffed up! One time it was the paperboy teasing her in the window anothertime it was a peeping tom! She will growl like a dog when that happens, she can be very protective.