Spam pays—that’s the bottom line. Economics, not technology, carries the day. Unlike surface mail, e-mail carries no incremental cost increases for larger volumes. Even if only 1 person in 1,000 responds to a solicitation for V1agr@ or L0west R4te Life Insurance, those businesses make money. More problematic from a consumer perspective is the impossibility of distinguishing a legitimate (albeit annoying) Internet business from an organized-crime spammer out to steal your credit-card information. As if that weren’t bad enough, sometimes the spam carries a virus or worm as a payload, intended to hijack or compromise your computer.

The economics have grown so overwhelming that more than 90% of e-mail traversing the Internet is spam. According to the ePrivacy Group, the volume of spam has been growing by 18% per month. The Internet service providers have a structural problem: The accidental blocking of legitimate e-mail messages irks customers even more than the receipt of bogus messages, and no tools can kill all spam without also eliminating some genuine mail.

"This situation has created an arms race between the spammers and spam blockers," says Daniel V. Klein of LoneWolf Systems, an authority in the field of e-mail security. "Spammers are smart—for every new anti-spam technique, there is a newer spam-sending technique." BusinessWeek Debate Room Spam: There’s No Canning It