From eWeek:
Money is the motivation for scam-spam. The motivation for clicking on it is far less straightforward, and none of us is immune.
“It’s not like certain people are going to be nailed by spam all the time. Or that there are certain motivations that will just [always] trigger people [who respond] to spam scams. It’s really the interplay between personality and motivation, emotion—all sorts of things,” said Dr. James Blascovich, professor of psychology at UC Santa Barbara and co-director of the university’s Research Center for Virtual Environments and Behavior.
“It’s a little more complex, but not much different from the complex interplay of psychological factors that get people to succumb to any sort of scam.” …
McAfee, of Santa Clara, Calif., throws around figures like these: If half of the population in the United States (about 150 million people) use e-mail on a daily basis, and if only half of them (75 million) are gullible, and only 1 percent (750,000) buy into scam-spam on a given day, and if those victims were to cough up a mere $20 per scam, the potential market amounts to $15 million a day, or $105 million per week, or nearly $5.5 billion per year in just the United States.