I just wanted to share an excellent case study of a "nigerian prisoner" con. Its a long article, but worth the read. A highlight is the mark's state of mind even after he realizes the con:

"I think they were legitimately trying to use me and my resources to get their funds out of Nigeria into a safe place where they could have access to them. Somehow there was a buyoff, a payoff, or something that went on there, and then it got switched to the point where I was then dealing with fraudsters.”

-- JustinColannino - 21 Feb 2008