Here is an interesting and informative video from the University of Washington Although it's a few years old I think it's still provides some good information, and an interesting comparison of the spam problem then (2005) and now. Here's an excerpt from the summary posted on Google Video:

A panel of legal experts discuss the issues from three vantage-points: what's currently being done to combat spam, how to avoid being perceived as a spammer by your customers, and future plans for eliminating spam. - ResearchChannel is a nonprofit media and technology organization that connects a global audience with the research and academic institutions whose developments, insights and discoveries affect our lives and futures.

Check it out and let me know what you think-unfortunately for some reason they refuse to allow their videos to be embedded so you'll have to check it out here at their website.