When Heather Armstrong’s mother left a rude message on her telephone answering machine the other day, Armstrong never hesitated. She posted the details word for word on her personal weblog. “Heather, this is your mother,” the message began. It ended: “You’re a shit-head. Call me back.”

By the outspoken standards of one of America’s most successful bloggers, it was actually quite a tame exchange. Armstrong once lost her job as a web page designer for using her blog to slag off her bosses. When she posted an abusive diatribe about her parents’ religion – Mormonism – her father did not speak to her for months.

Yet Armstrong’s readiness to air online the most intimate details of her family life have earned her the kind of following that many commercial websites would envy. With her site now recording 4m page views a month, she ranks 47th in popularity among the estimated 110m blogs on the internet.

Armstrong’s success as a funny, opinionated public diarist has not only earned her national attention and meetings with Hollywood agents, but is also fuelling a debate by psychologists over the possible long-term effects of a worldwide addiction to internet self-exposure.

Armstrong, a willowy 32-year-old blonde whose site was recently estimated to be worth up to $40,000 a month in advertising revenues, acknowledges that she has been feeling the strain of turning her life into a public spectacle.

Last week a parade of television crews marched into her home to interview her about her success, prompting her to post a brief new message on her blog: “Can’t update. Terrified.” She also acknowledged to The Wall Street Journal that she had begun to understand why “famous people turn to drugs or commit suicide”.

Her remarks followed the demise of another popular American blog whose author had begun to have serious doubts about exposing his family life online. Steve Almond, a Boston writer, ended his Baby Daddy blog last month after a series of hostile comments criticising his parenting style.

“I loved that so many people liked the blog and connected to it,” Almond said. “But we also want the family to have experiences that are inside the family.”

Visitors to Armstrong’s blog at dooce.com are greeted with the unpromising message: “This blog makes your butt look big.” Her posts often tackle subjects of numbing banality, such as what she bought at the grocery shop and how she hangs her pictures on the wall.

Yet she also writes with sometimes painful frankness about her feelings towards her family and has even admitted to the occasional negative thought about Leta, her four-year-old daughter. Her honesty has earned glowing praise from countless women who recognise that mothers cannot always be perfect. But she has also been wounded by vicious criticisms.

“The hate mail will invariably happen,” she told the Journal. “And when it does your entire world will crumble around your ears.”

Family therapists have begun to wonder about the possible effects of parental blogging on the psyches of children once they are old enough to understand what has been written about them. In an article entitled The Decline and Fall of the Private Self, Psychology Today magazine recently wondered if it was really healthy to “expose your struggles, fears and adventures to an audience”.

Many bloggers argue that openness and honesty are therapeutic. But some therapists fear that the most popular family bloggers may be writing themselves into a corner and may feel forced to make ever more intimate confessions or revelations so as to keep the lucrative audience they have acquired.

Armstrong’s blog has been so successful that her husband Jon has left his job to help her to manage it full-time. “She really doesn’t have the option of pulling the plug the way other people do,” said May Friedman, who is writing a book on parental bloggers.

Armstrong has made several adjustments to her approach since she started her blog. Scarred by the Mormonism breach with her parents, she has become more careful about how she describes her family.

Her mother’s answering machine message may have sounded combative, but it was part of a longer post in which Armstrong wrote: “I thought I would publicly declare how much I loved her despite our many differences.”

In recent weeks her blog has featured less controversial subjects, such as the time a raccoon got stuck in her chimney. Yet she still succumbs to startling asides, notably the post where she threatens to castrate her husband with nail clippers. She was joking, of course, but she admits that the pressure has taken a toll: “He and I have had our marital problems for sure and we go to therapy all the time.”