Cindy Cohn and Annalee Newitz at the EFF have written a very interesting and thoughtful paper on spam:
Noncommercial Email Lists:Collateral Damage in the Fight Against Spam, suggesting that non commercial mailing lists are suffering disproportionate "collateral damage" in the fight against spam.

My own organisation, the Open University, uses spam management filters and I'm grateful for these because I deal with tens of thousands of emails each year. The result of this avalanche of email is that unless an individual email gains my attention virtually immediately it gets deleted. And anything flagged by spam filters gets instantly deleted.

Cohn and Newitz are right to question the principles, processes and mechanics of spam filtering tools but just as we have information management systems in organisations to filter the right bits of paper and the right phone calls through to the most appropriate people we need information management systems in the electronic realm. How to square that with a sensitivity to be aware of and committment to avoid censorship and maintenance of the end to end architecture of the Net is a complex question to which there are no simple answers.