Blacklisting works like an embargo - andi it is our best reactive self-defense
It has been said before and it is touching some nerves - but brutal blacklisting is an active defense that works. Ok, some innocent services and services are also blocked but it is the only way to make it cristalclear to the guys who don't care about security upline or downline their business that they will lose much more business if they continue like this.
Look at the free .tk domain. It was a hotbed for spammers and crooks. But then it become blocked - just like .biz and .info (and .euro beginning) - as a whole without finetuning. If they don't clean up their act and don't invest time and effort in running a clean business why should be invest time in trying to make a difference between the good and the bad sites they are hosting. The .tk domain saw immediately the number of registrations falling and decided to take action and since than malwaresites are disappearing faster than re-appearing. The blockade of the .tk domain is more or less overkill now but only after a few weeks of total blockade by numerous servers and networks.
The other example is the Russian Business Network in the Ukraine. I think that after more or less a year security people got fed up with researching hundreds of domainnames and ip adresses and the rest to block and the decision was more or less taken by the antimalware fighters to block the whole ASN internetrange. Some good firms and sites would be hurt, but it would be the only way to make sure that if the hosters and ISP's that were selling their businesses to those crooks they would understand that they would faster than sooner be cut out of the internet. RBN has been cut out of the Ukrainan Internet by their ISP's and the blockade has been called to an end. Rumors are saying they will go to China. Well who needs .cn anyway ? Even the gov.cn sites are full of viruses, spam and crackers.
Maybe we should take out one malware hosters or ISP a month. All over the world. Blocking them out for at least a month untill they clean up their business. It will never end - sure - but maybe we shouldn't let the cancer develop itself like this and some operations are necessary to cut them out.