You are quite right. Such scams have indeed not only been around a long time, but quite a number of variations have been used. Besides the ones you mention, one of the more recent is impressive. They will tell you about someone who died and point you to a news article, often in very reputable publications, "proving" that person did in fact die in some accident or such. It never ceases to amaze me how creative these crooks can get, and to what lengths they will go to separate people from their money, or worse.
BTW, I noticed in my original post that the last line is missing, which will point readers to my complete list of
Business-Related Frauds & Scams online at /http://www.due.com/super/reference/index.cfm.
This of course includes the Nigerian scams, and a total of 96 frauds and scams.