Sloane Crosley may be smart and booky, but the "average person swallows X spiders per year" thing is not just false but a canonical example of the kind of absurd statement that people would believe because they'd read it on the Internet.

http://www.snopes.com/science/stats/spiders.asp

(Yes, I'm aware of the irony of referring people to a web site while asserting that one oughtn't believe what one reads there.)