Live and let spam is NOT a solution
I still have some trouble understanding how the so-called safe havens exist. The Internet is predicated upon cooperation. You refuse to cooperate in shutting down your spammers, why should I cooperate with you in such little things as accepting ANY of your email or allowing anyone to access any websites hosted in your network? It doesn't really matter if "you" is a nation, a corporation, or even a real person running a minor Web server. If you aren't willing to cooperate, you should be frozen out. Start with a few cold toes, but the other side should keep Mr Freeze's phone number handy...
Anyway, the current new annoying spam-scam of the day involves Yahoo's calendar, apparently via the German subsidiary of Yahoo. This one really screws with the filters, but that's fine with the spammers. After all, live and let spam has become part of the spammers' business model. When you think your marginal cost is effectively zero, there's no problem with another million spam messages. One more sucker? Divide by zero and the RoI still looks like infinity, and the marginal cost to all the other suckers is certainly not bothering the spammer's nap time.
I'll bounce a possible answer at you on the theory that you might have some personal friends and influence at Yahoo, possibly even including this Marissa Mayer person. I really would like to see Yahoo survive. Nothing personal about Yahoo, but just as a matter of giving us more meaningful freedom and for the sake of increasing the value of the Internet for all of us.
In the case of Yahoo, I think their focal point and the locus of any recovery has to be their email system. What is the #1 problem with email? SPAM. The spammers divide-by-zero economic models must be thoroughly broken. That's not to suggest that the spammers can ever become decent human beings. You don't have to be a sociopath to be a major businessman in America, but it is an absolute requirement to be a spammer. I'm just saying that we can and should push the spammers under less visible rocks, and the best way to do that is to make spamming much less profitable.
What I suggest is that Yahoo should integrate a REAL anti-spam system into their email system. Something like SpamCop, but on steroids. If you're familiar with SpamCop, you know that it does an automatic parse of the spam and asks for confirmation before sending complaints to the spammers' ISPs and webhosts. What I'm suggesting is several rounds of analysis and increasingly refined confirmations and targeting that would route complaints to ALL parts of the spammers' infrastructure, pursue and harass ALL of the spammers' accomplices, and help and protect ALL of the spammers' victims. Of course the webforms should always have "other" options for the spammers' new attempts, like this new calendar scam. The email system can give recognition for effective spam fighting--I just want to be a spam fighter first class. (I don't want to criticize SpamCop, but the truth is that they lost their fire after Cisco acquired them... I feel like they are no longer improving, but barely surviving.)
Let's remember that there are a LOT of people who hate spam and only a tiny number of idiots that send money to the spammers. If it is made easier for the large number of people to fight spam, then a few of them will join in, and that will immediately make it MUCH harder for the spammers to reach their suckers. Also remember that the spammers cannot obfuscate the parts of the spam that have to be understood by human beings.
Good luck, Mr. Phelps. If you fail to save Yahoo, the secretary will disavow any knowledge of your actions. If you succeed, the secretary would appreciate a tip of the hat in hopes of getting some leverage on other projects...