A lot of us like to laugh at those atrociously written / edited scam letters promising you vast riches of possibly-ill-gotten gains (you can't scam an honest man), if only you'll send your bank account info. They're so poorly crafted, with misspellings and grammar errors, and so implausible in their very subject, it must mean the scammers are just about as dimwitted as the hapless suckers they rope in.
Or … maybe not. It may be the scammers are just weeding out the less gullible in order to get the well-and-truly feeble-minded as their victims. After all, emailing is cheap, but time is money.
'By sending an email that repels all but the most gullible the scammer gets the most promising marks to self-select, and tilts the true to false positive ratio in his favor.'
http://research.microsoft.com/pubs/167719/whyfromnigeria.pdf
Maybe not so silly.
P. T. Barnum said it best: there's a sucker born every minute.