Sed quis decipiet ipsos Deceptodes?
No doubt most of you have come across - probably several times - the Nigerian 419 scammers (been there, done that, bought the T-shirt).
quisalan pointed me at this amusing example of someone scamming them right back. Not having actually read H.P. Lovecraft (although I am aware of the Cthulhu mythos via User Friendly etc.) I doubtless missed some of the finer points, but still found it highly entertaining.