As a child, Tim Berners-Lee was immersed in mathematics by his parents, who worked together on some of the earliest computer projects. The tuition worked. When he became a college student in the 1970s, Berners-Lee built his own computer by soldering a rudimentary processor to an old TV.

Two decades later, in 1991, he declared his genius to the world as the inventor of the world wide web, designing the first web browser and server. His creation was also the first web directory, allowing users to access information from other sites.

But this week Berners-Lee (now Sir Tim) issued a dire health warning on the reliability of the information swirling around his great invention. He slammed the sheer volume of malicious rumours and daft conspiracy theories being passed off as facts, describing how "the thinking of cults" has infested the knowledge base.

Outlining the dangers, he explained: "On the web, the thinking of cults can spread very rapidly and suddenly a cult which was 12 people who have deep personal issues can find a formula which is very believable. This can result in a conspiracy theory of sorts which you can imagine spreading to thousands of people and being deeply damaging."

Berners-Lee developed his ideas in the 1980s while working at CERN, the nuclear research hub that last week switched on its Large Hadron Collider, crashing particles together in an effort to uncover the secrets of the early universe. Despite the assurances of eminent scientists, an online campaign generated fears that the collider would turn into a doomsday machine, destroying the earth. Berners-Lee also cited a cyberspace disinformation campaign for spreading the false and damaging belief that the MMR vaccine can cause autism in children.

Other web rumours are false and damaging in a more personal sense, with celebrities inevitably an inviting target. One story stated as fact that the heiress Paris Hilton had been fatally stabbed when she was behind bars in LA, while another reported that actor Tom Hanks had plunged to his death while filming close to cliffs in New Zealand. In another infamous case, an elaborate hoax interview with Serena Williams reported the tennis star as saying that she only dated white men, comparing the average black man to "a poor homeless dog". She went on a number of TV and radio shows to express her disgust at the "vile" hoax perpetrated on her.

On a more frivolous note, another story still circulating long after it first appeared on a bogus BBC webpage claims that 42 unarmed members of the Cambodian Midget Fighting League were killed or injured when they took on an African lion in a bloody fight. The hot hoax of the moment is a photo of US Republican vice-presidential candidate Sarah Palin clad in a fetching bikini, toting a rifle.

The shot is a fake, but that hasn't stopped it generating millions of hits.

A host of other episodes are gathered in the book The Cult Of The Amateur by US author Andrew Keen, which makes a sweeping attack on the promiscuous knowledge culture of the internet.

Keen hits the usual targets, from porn to online poker, but his main thrust is that the web is dumbing itself down by replacing the authoritative knowledge of experts with the flawed "wisdom of the crowd".

He points an accusatory finger at the online encyclopedia Wikipedia, which relies on volunteer editors and contributors.

Wikipedia gets far more traffic than the Encyclopedia Britannica website, which relies on experts and scholars. The problem is that the interactive format employed by Wikipedia opens it to postings that are inaccurate, unverified and sometimes downright fraudulent.

Some time ago, it emerged that a contributor using the name Essjay, who had edited thousands of Wikipedia articles and had been given the authority to arbitrate disputes between writers, was a 24-year-old hoaxer named Ryan Jordan, and not the eminent professor he claimed to be. Most infamously, the venerable White House aide John Seigenthaler was slandered in a malicious Wikipedia biography that named him as a Kremlin spy complicit in the murders of both JFK and Bobby Kennedy.

Kean warns against a future where knowledge will be a debased currency and we will "live to see the bulk of our music coming from amateur garage bands, our movies and TV from glorified YouTubes, and our news made up of hyperactive celebrity gossip, served up as mere dressing for advertising". This is what happens, he insists, "when ignorance meets egoism meets bad taste meets mob rule".

Meanwhile, Sir Tim Berners-Lee believes it's not too late to save the internet from its cheap and nasty leanings.

This week, he said that his World Wide Web Foundation is preparing a mark of quality that will endorse sites which pass certain standards of reliability.

Dr Mel O Cinneide of the UCD School of Computer Science and Informatics is sceptical about Berners-Lee's chances of recorking the genie he has released.

"I don't see it. The web has its own existence," he says.

"It's a fact of human nature that people like gossiping.

"People have always told stories that are not true, and wanted to believe stories that are not true.

"There must be an understanding that you can't use a website like a newspaper. You can't read people's blogs and think they're gospel.

f you want, say, medical information you can cross-check a couple of websites of big American hospitals and you can be confident the information is good."

He points out that urban myths, playful spoofs and damned lies have always been with us.

"There's a famous story that was told 25 years ago about a mother who lost her little girl in a shopping mall, and the child is discovered in the toilets where someone has cut her hair to turn her into a boy.

Someone told me, as gospel truth, that that incident happened in Bunclody last weekend.

"People love a good story and don't tend to let the facts get in the way."

Despite the web's glaring flaws, Dr O Cinneide reasons: "It's a great resource, and I've never come across a spurious site that gave the impression it was otherwise.

"People who are experts in their field will tend to be busy, and are likely to post information that's short and to the point.

"People who appear to have too much time on their hands are probably not the most reliable sources of research."

- Damien Corless