Spam pollutes like 3 million cars. What about advertising?

A message on Slashdot brought my attention this morning. Spam uses 33 billion kilowatt hours of energy per year, which is to suit 2.4 million families or 3.1 cars. This comes from the 60 trillion "dumped" spam messages in 2008. So, not only it pollutes your mail box, but also environment. "Interestingly, the majority of energy usage (around 80%) comes from users viewing and deleting spam, and searching for legitimate emails within spam filters."

Interestingly, the research is made by an anti-spam corporation, and one of the main recommendations is to use spam filters (what a surprise!).

I was actually wondering if there can be such a research on the pollution coming from advertisement (online, but also billboards and posters, tv, electronic billboards, painting and stickers all around in the metro stations, on buildings, etc., etc.).