I have always wondered if that would work for spam too. What if we would set-up a bunch of servers to follow all links (times 10) in all spam messages. Even better, make it a plug-in for Outlook & Mail. Then, if a spammer would send out 100.000 messages he would immediately receive 1 million hits. No problem if you are authentically sending a few emails but a huge problem if you are sending out millions of mails.

If would be an active spam fighting solution instead of all the 'turn the other cheek' solutions that are popular right now...