It's been nearly a decade since spammers and their enemies begun evolving competitively. As with the classic cheetah/gazelle model originally formulated by Darwin, each time one group becomes a little faster or more agile, its adversaries develop traits for outwitting and outrunning it.

In addition to wasting people's time with unwanted e-mail, spam also eats up a lot of network bandwidth. Consequently, there are many organizations, as well as individuals, who have taken it upon themselves to fight spam with a variety of techniques. But because the Internet is public, there is really little that can be done to prevent spam, just as it is impossible to prevent junk mail.

Nobody wants it or ever asks for it. No one ever eats it; it is the first item to be pushed to the side when eating the entree. Sometimes it is actually tasty, like 1% of junk mail that is really useful to some people.

The number of unsolicted commercial electronic messages received by the average American in 2001 was 571, according to Jupiter Media Metrix. By 2006, Jupiter says, that number will increase to 1,400, with more than 206 billion spam messages going out over the course of the year. While these numbers are notoriously difficult to calculate, every survey and ISP record points to dramatic increases in spam, sometimes as much as 300 percent year over year. One reliable indicator of the problem's magnitude is the size of the anti-spam effort. The range of tools available to ISPs, enterprises and consumers in the fight against spam grew considerably during the Web bubble. Simultaneously, heavyweight Web marketers and interactive ad players have been scrambling to distinguish their services from the bad guys, as well as to counteract growing calls for government controls on digital marketing.

In one of the biggest such moves, the Direct Marketing Association (DMA), through its subsidiary, the Association of Interactive Marketing (AIM), has released online commercial solicitation guidelines in an effort to promote high ethical standards among marketers. The rules require that members let e-mail recipients know how they can refuse future mailings and allow consumers to prevent the sale or rental of their addresses