Yes, I said "industry". And this interview from Scam Detectives makes it clear that it is an organized, structured industry in Nigeria. (By way of Bruce Schneier)
Read directly at Scam detectives here, here, and here (three parts).
A choice excerpt:
Scam-Detective: John, I think you have been basically honest with me so far. Please don’t stop that now. You know as well as I do that not all of your victims were motivated by greed. I have seen plenty of scam emails that talk about dying widows who want to give their money to charity, or young people who are in refugee camps and need help to get out. You targetted vulnerable, charitable people as well as greedy businessmen, didn’t you? You didn’t care whether they could afford it or not, did you?
John: Ok, you are right. I am not proud of it but I had to feed my family.
Scam-Detective: And fund your BMW, mobile phones and laptops, let’s not forget about that. When the victim had run out of money and couldn’t send any more, was that the end of it? Or did you go back later for more?
John: We had something called the recovery approach. A few months after the original scam, we would approach the victim again, this time pretending to be from the FBI, or the Nigerian Authorities. The email would tell the victim that we had caught a scammer and had found all of the details of the original scam, and that the money could be recovered. Of course there would be fees involved as well. Victims would often pay up again to try and get their money back.
Scam-Detective: So when the victim had had some time to get over the fact that you had wormed your way into their lives, gained their trust and ripped them off, you went back for another bite of the cherry? The more I speak to you John, the less I like you.
John: I know, I know. Don’t be angry with me. I’m not proud of what I have done and I am very sorry for everyone who sent money. If I could give it back I would.
Scam-Detectives: But only if they sent you $1000 by Wire Transfer first?