I can understand the frustrations of receiving those rotten to the core spams. But hacking back into the spammer's system is still illegal. Two wrongs does not bring out a right. Maybe you can advise your friend against doing such things in the future as it is illegal. I would hate to see anything happen to your friend especially when dealing with such spammers. Maybe what he can do is to track down the information and report to the spammers upstream and let them handle the spammers.
But this is also a crime. Hacking in to someone else's system, Oops.. Whatever may be the reason. He has also to be punished.
Honestly no I dont think it is over the top.. Do you realize how many people get harmed and scammed out of money do to these spam and phishing emails.. I get daily emails say i won the UK lottery, and pay pal... many many people fall for these every day.. Then you got emails from Nigeria I know people that have lost thousands of dollars to these people. I wont tolerate spammers on my server, you spam your gone. Nationl Liverwood Lottery YOU HAVE WON £1,500,000 *CONGRATULATIONS* UK LOTTERY PROMOTION 2008 EDITION OFFICIAL PRIZE NOTIFICATION PayPal Attention! Your PayPal account has been limited!
Well, these emails aren't just spams but scams as well. For such scammers+spammers jail would be just nice for them. Though you will have to use tax payers' money to feed them in jail.
Oh no!... where I am going to get my viagra from now? Its amazing what you can get away with online... imagine if someone was dropping hundreds of unwanted flyers into your 'real' post office mail box every day. How long would that last?
It depends no the laws in their country. China is cracking down on warez, so they're probably cracking down on spammers too. I know that at one time, Gmail was blocking all mail from China because 90% of it was spam.