Electronic mail was the Internet's first killer app. Thanks to electronic junk mail, it could be the Net's last killer app as well.

Direct marketing professionals bristle at the words "junk mail." Roy Schwedelson, CEO of Florida-based Worldata Inc. - one of the nation's largest mailing list brokers - nearly hung up on me when I uttered the dreaded phrase in an interview. The reason is simple: Traditional marketers really don't want to send mail to people who don't want to receive it. It typically costs a marketer 50 cents to rent a person's name and address, print an advertisement, then send it to them. As one prominent direct marketer said, "There is no such thing as junk mail, only junk people."

But the Net's crazy economics changed all that. On the Net, it's just as cheap to send a hundred emails as it is to send ten. And if you're in the bulk mail business, it's just as easy to send ten million pieces of mail as it is to send a million. All you need is a list of email addresses, a connection, and some garden-variety robots and programs.

And it's getting worse, to the point where some people believe that if the trend continues unchecked, spam will overrun their mailboxes. This won't destroy the Net, but will make mail unusable for most people.

Already, a growing number of individuals and companies are spamming for hire. Following the lead from Jeff Slaton (aka the Spam King), these companies offer spams-for-hire. They thrive on shady businesses that don't know the first thing about getting online themselves.

I called one such company, Cyber Promotions, in Philadelphia, Pennsylvania, and was told that they charge US$149 for a five-line advertisement. This ad is bundled with 20 to 30 others and sent to the company's mailing list of 900,000 names. You can have your own "full-page ad" for $995.

Meanwhile, Jeff Slaton has gone from spamming to selling his own spamware. Doing business as Unix Etcetera - "We are Unix geeks with an attitude" - he is selling a program called Lightning Bolt. This package gleans email addresses from Usenet, collects them in a large database, then sends out the junk mail. Another piece of spamware out there is Floodgate: "The ultimate in email programs. Open the floodgates and let the email flow NOW!" blares the company's Web page.

Ian Kaplan, a programmer in California, recently contacted me to let me know what Slaton was up to. Kaplan's upset that folks like Slaton and Floodgate are distributing the tools that will let thousands of spammers flower on the Net. But he's also kind of pissed that these folks are making money with what are essentially trivial programs.

Fundamentally, there are three ways to put an end to spamming: technical, economic, and legal.