The industry’s VIPs mingle at political galas and Super Bowl parties. Their product is available on mobile phones, podcasts, and particularly the internet – there it is an attraction like no other, patronised by tens of millions of Americans.

It is pornography. And if you are a consumer, John Harmer thinks you are damaging your brain.

"Some people lie about it," Cambria said. "It’s their way of excusing personally unacceptable conduct – ‘It wasn’t me, it was porn’."

Such attitudes infuriate experts on the other side who say online porn is as addictive as crack cocaine.

"The internet is the perfect delivery system for anti-social behaviour – it’s free, it’s piped into your house," said Mary Anne Layden, a psychologist and addiction expert at the University of Pennsylvania. "Internet porn is probably the biggest miseducation system we can devise in terms of sexuality, misuse of women."

She says many of her patients, rather than improving their sex lives with porn, suffer sexual dysfunction.

Interest in porn is age-old and normal, says psychologist David Greenfield of West Hartford, Connecticut, an expert on internet behaviours, but it can become a destructive obsession for a minority who indulge in it at the expense of healthy relationships. Easy availability is part of the issue.

"It’s not your father’s porn," he said. "With little or no effort, as long as you have a computer, you can access some of the most stimulating content on the planet. There’s no delay, no person watching. It’s designed to very quickly get to a point where you’re not in full control."

He estimates that for up to 10 per cent of porn users, relationships suffer – with many husbands spending so much time online that they cease to have sex with their wives.

Divorce lawyers report that porn use is an increasingly common factor in marriage breakups: It can cause immense pain when a wife discovers her husband’s porn habit.

"I compare it to your house burning down," said Laurie Hall, who divorced her husband after writing a book called An Affair of the Mind, about his 20-year obsession with porn.

"It destroys your sense of personhood when you bring all that you are into a relationship and someone chooses to ignore that," she said. "It eats away at the heart of the family."

Across America, compulsive porn use has spawned hundreds of support groups, treatment programs and web sites where heartbroken spouses – mostly wives – swap stories of their mates’ obsessions.

Polls suggest most Americans believe porn should be off-limits to minors and available legally for adults. But groups such as Morality in Media think the public favours tougher enforcement of obscenity laws against hard-core porn; it operates a web site that forwards obscenity complaints to federal officials.

"We’re not going to get rid of all of it, but we can push it back into the gutter as far as humanly possible," said Morality in Media president Robert Peters, a Dartmouth-educated attorney who struggled in his 20s to kick a porn habit that started in grade school.

"It was hell," said Peters, recalling a six-year stretch where he regularly visited porn outlets on New York’s 42nd Street. "It’s a very hard habit to break."

Mark Laaser of Eden Prairie, Minnesota, says he frequently sought out pornography and engaged in extramarital sex for more than 20 years, starting in college and continuing through a career as pastor and counsellor. He now runs workshops, and consults with church congregations on the issue.

"I’ve seen the damage it does to marriages, to families," he said.
Though he stressed the need for individual willpower, Laaser also faulted the porn industry for employing aggressive online technologies that "besiege you."

"Sometimes it’s not a matter of free will," he said. "It’s a matter of invasion."

Another self-described former addict is Phil Burress, head of a Cincinnati-based conservative group called Citizens for Community Values.

Like many conservatives, he had hopes that the Bush administration would reverse Clinton White House policy and step up prosecutions of adult-porn obscenity cases as well as child porn cases. Thus far, Burress is disappointed.

"Five years into this administration, they get an F," a failing grade, he said.

Still, Burress is encouraged by the recent formation of an FBI anti-obscenity squad and the appointment of Brent Ward, a former US attorney who combated porn in Utah, to head an obscenity prosecution task force.

The Justice Department defends its record, saying it has indicted dozens of people on obscenity charges since 2001 and suggesting the pace will increase. But with a vast array of potential targets, and many other priorities, prosecutors must choose their battles carefully.

One pending case involves obscenity charges against a California couple whose company sold pornographic videos depicting simulated rape and murder. The charges carry a maximum penalty of 50 years in prison plus $US7.5 million ($A10.49 million) in fines.

The bottom line, perhaps, is that each side in the debate can make points that seem unassailable.

"Everyone agrees that tens of millions of Americans consume porn. … ministers, PTA members, policemen, teachers, soldiers, dentists and Boy Scout leaders," argues California sex therapist Marty Klein. "The overwhelming majority of them don’t rape strangers or emotionally abandon their wives."

But Layden, the Penn addiction expert, refuses to see porn as mostly harmless.

"When I ask men who are sex addicts if they would want their wife or daughter to be in porn, 100 per cent say, ‘No’," she said. "They want it to be somebody else’s wife or daughter. They know this material is damaging."

– AP