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In 1768, three Scottish printers began publishing an "integrated compendium of knowledge" which they called Encyclopaedia Britannica.

In 1920 it was bought by Sears Roebuck, the American mail-order company and moved its headquarters to Chicago.

In 1941 ownership passed to William Benton, who later bequeathed it to the Benton foundation, a US-based charity. EB grew into a profitable enterprise whose product was regarded as the gold standard for accuracy and comprehensiveness. By 1990 sales revenues had reached US$650 million ($1094 million).

Yet within five years, EB underwent a near-death experience. What almost killed it was a product most of its executives regarded as a joke, an encyclopaedia on CD-Rom launched by Microsoft and called Encarta.

The original content was licensed from an outfit with the Dickensian name of Funk and Wagnalls, and some of it gave trash a bad name. So Microsoft spruced it up, added multimedia content and made it easy to use. To the astonishment of EB's board, this meretricious object triggered a precipitous decline in sales of their gold-standard product.

Faced with catastrophe, the Benton foundation put EB up for sale.

It took 18 months to find a buyer, a Swiss billionaire named Jacob Safra who bought the company for half its book value. Full print sets of the EB are still available, as well as an online edition.

The story of Britannica is now a business-school case study in how rapidly competitors can emerge - apparently from nowhere - in a digital world.

The First Rule of Business nowadays is that somewhere out there someone (and not just Google) is incubating a business plan that is based on eating your lunch.

But the story continues. Last week Microsoft announced it would be closing all its Encarta websites (with the exception, for some reason, of the Japanese one) at the end of 2009, and discontinuing sales of Student and Encarta Premium software products worldwide in just two months' time.

Why? Well, the company explained on the website: "Encarta has been a popular product around the world for many years. However, the category of traditional encyclopaedias and reference material has changed. People today seek and consume information in considerably different ways than in years past."

Translation: Wikipedia ate our lunch. To see why, log on to Wikipedia and search for "Britannica". Shortly after the announcement, a new paragraph had been added to the lead-in material to the entry. "In March 2009," it read, "Microsoft announced it was discontinuing the Encarta disc and online versions." QED.

Wikipedia's ability to respond instantly to developments is just one of the reasons it has transformed the world of reference works.

Another is its sheer scale.

I've just checked the main page and it is reporting that the English version currently has 2,822,233 articles.

Yet another is its linguistic diversity - 875,000 articles in German, 774,000 in French, 568,000 in Chinese, 585,000 in Polish etc.

There is no way a conventional, centrally edited, commercially financed operation could match this.

The idea that a useful, serious reference work could emerge from the contributions of thousands of "ordinary" internet users, many without scholarly qualifications, would until comparatively recently have been dismissed as absurd.

Unwillingness to entertain the notion that Wikipedia might fly is a symptom of what the legal scholar James Boyle calls "cultural agoraphobia" - our prevailing fear of openness.

Like all phobias it's irrational, so is immune to evidence. I'm tired of listening to brain-dead dinner-party complaints about how "inaccurate" Wikipedia is.

I'm bored to death by endless accounts of slurs or libels suffered by a few famous individuals at the hands of Wikipedia vandals.

And if anyone ever claims again that the entries in Wikipedia are written by clueless amateurs, I will hit them with a list of experts who curate material in their specialisms. And remind them of Professor Peter Murray-Rust's comment to a conference in Oxford: "The bit of Wikipedia that I wrote is correct."

Of course Wikipedia has flaws, show me something that doesn't.

Of course it suffers from vandalism and nutters who contribute stuff to it.

But instead of complaining about errors, academics ought to be in there fixing them.

Wikipedia is one of the greatest inventions we have. Isn't it time we accepted it? Microsoft has.