I read a great MediaPost article (requires free sign-in) by David Atlas, an executive from Goodmail systems. David outlines the ideal spam/complaint feedback system, and I think he has hit the nail on the head.
David contends that the current email complaint system lacks accuracy, granularity and security. For instance, one person clicking the spam button 10 times generates the same number of complaints as 10 people who each click once; recipients can't register the nature of their complaints, which accrue to IP addresses rather than senders; and the system doesn't protect against falsely-generated complaints.
He says the ideal system would be sender-based rather than IP-based. People would only be allowed to complain once per message, and frequency would be accounted for. The system also would also differentiate between complaints for commercial vs. transactional messages, by domain, and allow recipients to specify why they are complaining and what they would like to do about it. Both recipients and senders also would be protected against abuses of the system.
A reputation system based on this kind of complaint mechanism would benefit everyone. Senders would get better feedback and a more equitable allocation of emailing privileges, and consumers would get more relevant messages.
Sort of like Babe Ruth's fabled finger pointing out his home run before he hit it, perhaps David's article will point ISPs and ESPs in a direction of more accurate and more accountable complaint management.