The folks at WebpageFX Weekly have put together quite the infographic explaining the environmental cost of SPAM. I've written before about SPAM and the email industry… and am still surprised that no one has made any advancements in combatting SPAM.
If ISPs like Google, Yahoo! and Microsoft truly wanted to rid theirselves of SPAM, they would offer protected email addresses where the ISP (Internet Service Provider) controlled the opt-in methodology rather than the ESP (Email Service Provider). This would allow them to block any other source. But alas… we're stuck with a 20 year old system that doesn't appear to be improving anytime soon.