Poynton's
Anti-SPAM pageSPAM is unsolicited junk in your electronic mailbox. SPAM has reached epidemic proportions; it is estimated that well over half of all email traffic worldwide is SPAM. Borderline products and services that cannot be effectively marketed through conventional commercial means are advertised using SPAM because millions of messages can be transmitted at a cost to the sender of less than a penny each. Just like bulk or broadcast fax, the cost is passed on (without consent) to the recipient. (SPAM also includes numerous repetitive posts in Usenet newsgroups, but since so few people read Usenet news anymore, and since the quality of Usenet postings has fallen so low, I won't discuss that any more here.)
Eventually, SPAM will be prohibited through legislation, but that will take a long, long time, because (a) our lawmakers are clueless regarding technology, and (b) the problem is international in scope, with many many offshore spammers.
For an introduction: