Just for kicks, I've embarked upon a large spam and blacklist tracking project. Wondering how well Spamhaus works? Preliminary results are showing me that it's actually very accurate and has a much better (lower) false positive rate than every other blacklist I've tested. At the other side of the spectrum, Fiveten blocks nearly a third of desired mail, and isn't as good at tagging spam. Read more about it, and link to the actual data I'm publishing every day, over here on dnsbl.com.