Unfortunately spam is a part of life. Making it illegal is just a very bad bad idea. [ the whole freedom of speech thing and all... ] Finding ways to deal with it creates jobs anyways
. For those of us poor admins, it is a pain, but not really that tough. Dealing with the Messenger spam is pretty easy - just set your firewall to block that port before anything even gets into your network.
If anyone is wondering why spammers spam... it's because it works. People buy things from spam and they make money. The best thing to do is to buy whatever it is from someone else who doesn't spam.
If you're looking to find the IP addresses of people, try using something like the Ethereal Network Analyzer at http://www.ethereal.com/ or check out http://winpcap.mirror.ethereal.com for WinPcap. Check into the logs and you've got 'em. Personally, I use Ethereal. Works well for what I need.
If you're looking for vengeance, there are lots of ways to get it. I'll let the interested party(s) there do their own homework. Try googling "satanic voodoo rituals". Make sure to have a few extra live chickens handy.
Glad that little tid-bit helped a few people anyways. (There are people out there selling "software" to deal with the problem... hahaha... what a joke.)