Does the average person consume four spiders per year in his sleep?

For a spider to get into your mouth while you're sleeping, (a) you must have your mouth OPEN, which is certainly not universal, so there's a big chunk of people who can never swallow anything; (b) there has to be a wandering spider in your immediate vicinity, also something which--for most people in the civilized world, at least--is a fairly rare occurrence; (c) the spider has to either jump or fall into your mouth from a long distance, because they won't go near your mouth otherwise (they're not suicidal), and the odds are pretty astronomical of a spider randomly dropping into your mouth from the ceiling.Put it all together, and it would be a miracle for a spider to end up in anyone's mouth while they're sleeping, except for one rare circumstance--when a spider egg sac hatches indoors.

The Straight Dope Mailbag: The Straight Dope Mailbag: Does the average person consume four spiders per year in his sleep?