You decide that your friend might be on to something, so you send an e-mail to the 100 people in your personal e-mail address book with the subject line, "These Blueberry Muffins Have Been Described as Heaven -- You Can Have the Recipe for $5!" Your e-mail contains a link to your blueberry muffin Web site. As a result of your 100 e-mails, you get two orders and make $10.
"Wow!" you think, "It cost me nothing to send those 100 e-mails, and I made $10. If I sent 1,000 e-mails I could make $100. If I sent a million e-mails I could make $100,000! I wonder where I could get a million e-mail addresses..."