Interesting read here about attempts to hit back at spammers by Lycos, IBM and others, thus taking a pretty aggressive approach at spammers rather than sitting back and taking the heat as they say :

http://www.heise.de/...ewsticker/news/53697

http://spamkings.oreilly.com/...mmer_begs_for_1.html

Obviously the issue with fighting back is making sure you hit back at the appropriate culprits and don't lash out at innocent parties that may have been hijacked to carry out spamming...
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