Don't believe all these letters could be a scam? Well, using a tip from a scambaiter, I went to Google and typed in "guestbook guymen". Then, I proceeded to post my newly created, disposable e-mail address to about 30 or so guestbooks. The Nigerian Scammers use guestbooks as one tool to gather e-mail addresses. They post a message using the word "guymen" or "mugu" to alert other scammers that it's "their" guestbook to use to spam and scam the posters.
I started posting around 7:30AM on March 19. I received more than TWENTY scam e-mails that day, and more than THIRTY the next day, March 20.