Fighting Spam: An Alternative Approach
In the bigger picture, Banister's Bonded Sender idea is validation of the notion that whitelists could play an increasingly important role on smacking down spam. But in order for whitelists to reliably extend their utility to the rest of us (and not just companies that can afford to put up thousands of dollars in bond money), we'll need established methodologies and techniques that don't reproduce the kind of problems caused by blacklists--ones that don't throw the baby out with the bath water.
In this ZDNet article, David Berlind contends that certifying "good" email rather then eliminating "bad" email is the best solution for fighting spam. Read the article and you decide.