Jimmy Wales seems distracted. He checks his phone, stares at the ceiling, at the table, and checks his phone again. I assume, initially, that this is how he generally conducts meetings, but it turns out there's a reason: his second child is late arriving, and "we're pacing the floors." "We" is he and Kate Garvey, late of Number 10, where she was Tony Blair's diary secretary (as he reminds me, proudly) and now a director at Freud communications; they met at Davos a couple of years ago, and now he's moving to Britain to be with her. He will still commute to Florida, where his first daughter lives with her mother, every second week, as well as taking frequent trips all over the world, especially to India, where he is setting up Wikipedia's first office outside the US.

It's a surprise, in a way, that this is the company's first outpost. Wikipedia, which turned 10 last month, often seems completely ubiquitous. Plug any word into the internet – pylon, griffin, moonwalk – and there Wikipedia is, eagerly offering its services. And not just in English: the encyclopedia currently exists in 278 languages, from Kalmyk to Crimean Tatar, Sanskrit to Inuktitut. It is viewed by more than 400 million people a month, and 11.6m edits are made on its articles every month (it is, after all, "the free encyclopedia that anyone can edit"). And all of them will now know exactly what the co-founder (or founder – it's disputed territory) of Wikipedia looks like: the not-for-profit concern has just come to the end of its annual fundraising drive. Tests had shown that if they put Wales's face on the appeals, as opposed to anyone else, or nothing at all, they got twice the response. So there he was, any time you looked anything up – pensive, smiling, matey, gazing into the distance, or some combination of the above – and asking for money.

"We raised $16m (£10m) in 59 days, the fastest ever." Wales is bright and thoughtful, "smart" in the American sense of the word, like "a young Billy Crystal," as the writer Stacy Schiff once put it, "with the neuroses neatly tucked in". Certainly, he claims not to be neurotic – "I don't worry. It's just not in my nature, really" – and has a good line in the deliberately bland: to hear him describe the internet, and Wikipedia, is to hear a tale of public spiritedness, of millions of people working towards a common good, even though he must know that the thing he heads is far stranger and less dependable than that.

True, it must instil some faith in humanity to know that $16m arrived in donations averaging about £20. And then there's the way Wikipedia works day to day, with millions of unpaid contributors adding their tuppence-worth of knowledge to the site, or improving or disproving or contradicting or expanding someone else's tuppence-worth, mostly in the belief that it is worth doing so for itself alone. But not all people behave like that, and they have to be policed. Wales may spend his days evangelising (his word, despite his discomfort with its religious overtones) in Armenia or Azerbaijan, hobnobbing in Davos and generally being the suave public face of his company, but he still does some of the nitty-gritty, of keeping an eye on new entries, vetting the quality of their sources, flagging up inappropriate bias (an avowed Objectivist, he aims to excise all possible prejudice – and if that's not viable, to be as openly even-handed as possible), and reverting anything dubious. So the day before we met, Wales, who has along the way taken up the House of Lords as his expert subject, mediated in a discussion about what exactly to call Patience Wheatcroft, editor of the Wall Street Journal Europe, who has just been made a baroness. "And I reverted some vandalism." Some wag had decided to point out that Mervyn Davies, Baron Davies of Abersoch, "'is some joke mannnnn,' with about 5 ns – it stayed in for a few minutes and I took it out."

A lot of vandalism is of this sort. "We call it sandboxing – people are treating it like a sandbox – they know they can't really hurt anything." But some is far more serious – libellous, or (something of a favourite) premature expiry: Senator Edward Kennedy, in a famous example, was bumped off months before he actually died. When anything big bursts into the news – the recent shooting of congresswoman Gabrielle Giffords, for instance – regular contributors and "admins" rally instantly around the page, to protect it "and make sure nobody does anything stupid". Sometimes it has to be temporarily locked down. And it isn't always rogues. For a while, the whole house of representatives was regularly banned, because staffers were being deployed to massage voting records and biographical details, and present their bosses in the best possible light. Paul Dacre of the Daily Mail has reportedly done the same thing. Wales himself was accused of intervening in his own biography 18 times in one year, though he eventually repented, to the extent that, for a long time, it gave him the wrong birthday. "They got it from Britannica," he once said, "and Britannica got it wrong."

For Wales, this only reinforces a point of principle. "You shouldn't really use Wikipedia as the sole source for anything, ever. You shouldn't use anything as the sole source for anything, in my view." He is, in fact, generally dismissive of traditional modes of authority – peer-reviewed journals, the requirement for strings of letters after names. "I think people have to recognise that the traditional modes of authority weren't that great." It's fighting talk, particularly when you know that lurking in the background is a dispute with the man who helped him set up Wikipedia, Larry Sanger, who eventually couldn't bear the fact that the entries had no final, expert arbiter. Wales would rather, unsurprisingly, move things on. "To me, this question of 'Is Wikipedia reliable or not?' is sort of the five-year-ago version of the question. The contemporary version of the question is, 'Gee, this is actually fairly amazing, it's pretty good, how can we improve it? Where does it break down?'"

Authority, in his upbeat formulation, comes from something else entirely – from the sheer number of voices, the sheer variety of viewpoints, all hopefully deploying reasoned, well-buttressed argument (he is, above all, a believer in reason). At its most high-minded and impressive, this can take the form of a kind of hammering out, word by word, if necessary – even comma by comma, in cases such as Israel-Palestine or global warming – of a document that could be arrived at in no other way, apart, perhaps, from at the UN. And every single change is tracked in the edit pages that accompany each entry – what the change was, who made it, and at exactly what time.

At its least impressive, though, it simply results in "edit wars", in which people increasingly ill-temperedly revert, rerevert, and rerererevert facts they disagree with. A page called "Lamest edit wars" chronicles some of the silliest. Wales's profile echoes, in many ways, that of a typical contributor: 85% are male, generally well-educated, and often computer programmers, a scenario which he admits skews the way topics are chosen and treated on the site; the next three years, he says, will be dedicated to working out how to persuade other constituencies to join in too. He grew up in Huntsville, Alabama, where his father managed a grocery and his mother and grandmother ran a small private school that he attended. He describes himself as a "super-geek" with thick glasses and a very early interest in computers (it helped that his uncle ran a computer store), who read the encyclopaedia for fun. "I spent hours going through it, following from one entry to the next. 'See also' – and you'd read that. 'See also' – you could get lost in there." His mother had bought it from a travelling salesman when her eldest son was about three, and each year an envelope arrived, containing stickers on which were written that year's advances in knowledge; together they pasted them onto the appropriate pages, unknowingly foreshadowing the unimaginably speeded-up way in which Wikipedia now works. When he was older, he also entertained himself by writing code.

Married at 20, he studied finance to PhD level, then dropped out before writing his doctoral dissertation. A job speculating on interest-rate and foreign-currency fluctuations made him wealthy enough not to need to earn anything for the rest of his life, but an internet startup called Bomis was what actually provided the money to start Nupedia, an internet encyclopedia with exhaustively peer-reviewed entries, and then Wikipedia. He has not lost the knack of making money: he is also chairman of Wikia, a "wiki farm" ("wiki" means "fast", in Hawaiian, and technically refers to a website that can be edited by anybody) that hosts ad-supported wikis about any subject – the latest of which is going to be an Olympics wiki. (Garvey, who may by then be his third wife – they are engaged – is handling the Olympics account for Freud; between them they will do quite well out of the games.)

Some protest that while he gets to be a high-minded flagbearer for the free internet with Wikipedia – he insists that although he could make something in the region of $5billion from it, he has never ever been tempted – Wikia in effect piggybacks on the reputation built up by the legions of unpaid contributors to the encyclopedia, and thus ruthlessly exploits them. He dismisses this with the same, not quite convincing, argument that Arianna Huffington uses about the Huffington Post: "you're providing a platform and people can come and participate or not. If you enjoy it, you should do it. If you don't enjoy it, go do something else. It's completely fine. So that idea of exploitation doesn't make any sense to me at all."

He would rather tell a story of anti-exploitation, of freedom of expression – as in China, for example, which blocked Wikipedia altogether for three years (they still filter certain pages). People found their way around the firewall regardless, which is not in itself illegal, and proceeded to write entries in Chinese languages. Once they'd gone to all that bother, were the entries quite political? "No, no. They're mostly computer geeks – so they would write about computers. Star Trek and Star Wars. We do find we have a certain geek culture that transcends national culture."

It's the dawn of the Twitter revolution, according to some – "I think that's often overblown." Overblown, too, he thinks, are arguments by people such as Malcolm Gladwell, who recently wrote a New Yorker essay decrying what some people now call "clicktivism", where a click on a Facebook page or Twitter account replaces real activism. "Valid point, but I think it misses what's going on. I think you can't discount how incredible the impact is of people having access to knowledge, so they are aware of different ways of living, and they are aware of different possibilities for the future, and they begin to have a belief that 'Gee, actually, this country is allegedly a democracy, and we all know it isn't – it's time to demand change.' And that's no simple thing – it's about Wikipedia, it's about blogs, it's about news headlines from overseas – that flow of information, and people having more of a consciousness about what's possible in the world."