Why Spam Won’t Go Away
Spam is filling up the Internet, and it’s not going away anytime soon. It’s not just e-mail. We have voice-over-IP spam, instant message spam, cellphone text message spam, blog comment spam and Usenet newsgroup spam. And, if you think broadly enough, these computer-network spam delivery mechanisms join the ranks of computer telemarketing (phone spam), junk mail (paper spam), billboards (visual space spam) and cars driving through town with megaphones (audio spam). It’s all basically the same thing–unsolicited marketing messages–and only by understanding the problem at this level of generality can we discuss solutions.
http://www.forbes.com/2006/12/11/spam-security-email-tech-security-cz_bs_1212spam.html