Uh, they use Nigeria because that's where they are from. I saw a special (I think it was 20/20) awhile back and the story was about how Nigerian scammers came about. A lot of them are out of work guys who hang out in cafes setting up their scams. Sometimes they work with accomplices in other countries. However, most Nigerian scams have to do with finding long lost money, not so much about buying/selling equipment. Guess they are getting more sophisticated.