A story in Tuesday's New York Times about a "professional outdoorsman" who found a black widow spider in his shoe (after he felt it bite him) will ensure that you will never again not shake out your shoes.
I donned the shoes before walking to the edge of the water. Within about a dozen steps, I felt a stinging sensation on the second toe of my left foot, as if there had been a thorn inside the shoe. Then the pain increased to about that of a wasp’s sting. I sat on a rock and removed the shoe. The squashed remains of a spider were smeared across the insole. I realized instantly what must have happened: a black widow from the porch had made its home in my shoe.
Now ease your paranoia by watching this video of a person safely handling a black widow.