...fighting spam at the source is even better. When McColo, a major source of online spam, was taken offline in late 2008, the energysaved in the ensuing lull before spammers rebuilt their sending capacity equated to taking 2.2 million cars off the road...
http://www.c0t0d0s0.org/archives/5733-The-carbon-footprint-of-spam.html
...late 2008, McColo, a major source of online spam, was taken offline and global spam volume dropped 70 percent. The energysaved in the ensuing lull before spammers rebuilt their sending capacity, equated to taking 2.2 million cars off the road...
http://www.itbinternet.com/pr/26569