I've had a similar "dilution" system on my website for years, but this is for spammers harvesting email addresses. At the bottom of the page at
Another nice idea is "honey pots" where spammers harvest the addresses, then, when they send to it, they are added to block lists. I haven't done this as yet, though.
Harold
[TELECOM Digest Editor's Note: I do the same thing on the web page for this Digest