As much as you laugh at these, the Nigerian scammers have turned this into a billions-with-a-b dollar per year industry.  
In Nigeria, the 4-year-old Economic and Financial Crimes Commission says it has successfully cracked down on the large majority of home-grown scammers and has recovered more than $750 million for victims all over the world. 
And, believe it or not, the people that fall for the 419 scam the most are rich.
/I work with a former secret service guy that was the head of the task force against these scumbags