Teaching a little lesson on critical thinking and reading for information, I had students skim over a 419 scam email, without telling them its nature, and had them highlight the passages that would help them answer the question, "Is this a good deal?" We discussed what we'd highlighted, and then I told them to use a different color to mark any "red flags." (I was amazed at how many had never heard the idiom.)
Finally, the jig was up, and I told them that I'd received the spam in my email that morning, and that it was a complete and total fraud. Some of them were glad to have their suspicions confirmed, while others were totally shocked that someone could lie so blatantly in an email. In the end, the lesson worked on two levels: as a way to focus their reading, and as a way to keep them from losing big bucks to a crafty sleazeball.
If only this U.S. attorney had taken my class.