Why not respond to the scammers automatically?  You could put together a library of responses, use machine learning techniques to choose a response based on the spammer's initial email and recent message, and really put a dent in their productivity.<p>You could even send out spam messages of your own or resend the spammer's initial message and harvest the responses to use in the library.<p>It would be easy for Google and other email providers to do this with their collection of abandoned email accounts.