Surprisingly good reporting in the mainstream media (specifically, the Washington Post) about how shutting down McColo reduced worldwide spam volume by 65%.
Here’s a choice quote about why spammers prefer to host their servers in the United States:
What’s more, dependability and server uptime are important in cutthroat businesses for which an outage of a few hours can staunch the flow of spam and cost thousands of dollars.
Hey, business is business, even for evil spammers.