Osirusoft Blacklists The World
HUNDREDS OF THOUSANDS of spam emails, OVER AND OVEr.. consumes bandwidth, cleanup AND has been known to knock machines off line from the sheer amount of crap.
You try running a mail server, even at a small ISP, and see how much crap you have to deal with.
I've done it. My point is that while blacklisting can have it's uses, there's two big problems with spews:
a) They blacklist people specifically to cause harm.
b) USING ANY BLACKLIST AS A CATCHALL IS STUPID. Nobody should be doing this, and anybody who is should be fired for incompetence. It takes more than 'Some group of people who have nothing to do with us have decided that there's a small chance that this could be spam' to efficiently block spam.
SpamAssassin seems to have this down; give everything a score, and if it has a high enough score, then you can block it. But trusting a single source whose purpose is to hurt spam rather than to efficiently block it and only it, and using that as a sole source, like so so so so so many people do, is just plain fucking idiotic.