How can a Nigerian scammer tell, just by looking at thousands of e-mail addresses, who is gullible and who is not? He can’t. Gullibility is in this case an unobservable trait. But, Herley realized, the scammer can invite the gullible people to reveal themselves. How? By sending out such a ridiculous letter—including prominent mentions of Nigeria—that only a gullible person would take it seriously.
