Everything has a carbon footprint these days. Now spam does. I've read before what enormous energy drains some of the data centers are with their gazillion computers running. If there is, say, one spam message per real message, then the data centers have to double their storage capacity. (Those are example figures only.) Spam has real and significant impact of the receiving end and costs the spammers little to nothing.

[As a sidebar, I'd be perfectly willing to pay a penny per email, if the spammers had to also. That would mean nothing to me but would break the economy of spam.]

Back to the story: McAfee commissioned a study, the outcome of which was that a spam message as a footprint of 0.3 grams of carbon dioxide. Not much, except that the report says that there are 62 trillion spam messages/year, and equates that total to the energy use of 2.4 million homes (33 billion kilowatt-hours of electricity) or 3.1 million cars (2 billion gallons of gasoline) . Here is the story and the actual report (PDF).