The real long-term solution is to force all the major ISPs to maintain a growing catalog of all the domains and server addresses that engage in spamming, and give all the users the option to automatically reject all such e-mail (not just put the e-mail in a "junk" folder, but the option to drop it on the floor completely). Furthermore, anyone who is caught "spoofing" with a phony originator should be subjected to even harsher penalties than regular run-of-the-mill spammers.
Stop right there. I can't endorse any solution that forces any law-abiding party to do anything. The solution is to make spammers criminally and civilly liable for their theft of recipients' coumputer and networking resources.