"I have a new e-mail address," my 10-year-old daughter wrote in a recent message to friends and relatives. "My mom changed it from my old one because I was getting weird and disgusting messages from college girls who wanted a date with me! Gross!"

I did not see Francine's note for several days because my anti-spam software, not recognizing her new address, dropped it into the "Challenged Mail" folder. There it languished, waiting for me to "Allow Sender" or for her to verify that she was a human being rather than an automated mailer.

These are the twin pitfalls of fighting spam: keeping out too little and keeping out too much. Striking the right balance can be tricky, but it's not likely that new anti-spam legislation, several versions of which have been introduced in Congress, will make the challenge any easier.

For one thing, the right balance depends on preferences that vary from one individual to another. Some Internet users may want to err on the side of inclusion, tolerating a certain amount of annoying or offensive mail so as not to miss the occasional uninvited yet useful message. Others may be willing to sacrifice unexpected benefits for the sake of a pristine in-box.

Banning unsolicited e-mail would criminalize a lot of valuable (and constitutionally protected) communication, and limiting the ban to commercial messages is hard to justify.

Political and religious appeals can be just as irritating (if not more so), and people do sometimes take advantage of products or services offered by e-mail, just as they sometimes welcome the catalogs or credit card offers they get in their paper mail.

If there's a crucial difference between spam and ordinary junk mail, it's a difference in degree rather than kind. Both forms of solicitation impose costs on the recipients, who have to sort out the wheat and dispose of the chaff. But because sending e-mail is so cheap, online marketers have much less incentive to target their messages: Why winnow a list down to 1,000 likely prospects when it costs nothing more to e-mail 1 million?

The costs of spam are paid mostly by Internet service providers (ISPs), which are forced to invest in extra capacity and maintain filtering systems, and Internet users, who have to spend time downloading and deleting unwanted messages or waiting for their anti-spam software to do the job. According to various estimates, spam accounts for 40 percent to 75 percent of e-mail traffic. The cost in terms of lost productivity and countermeasures may amount to billions of dollars a year.

Naturally, people do not like bearing these costs, but the principle at stake is not obvious. To characterize spam as a trespass seems odd, especially since the law does not treat paper in one's physical mailbox that way. Perhaps uninvited communication is simply the price you pay for being connected to a network. Continued...