It's only when Wikipedia isn't there you realise how incredibly influential it has become.

Just try a few random searches. Yesterday I Googled "Scottish independence referendum" and top of the results list was the Wikipedia entry. Then I searched "global warming", which also served up Wikipedia's page as number one. Even searching something relatively obscure, like "pensions crisis", Wikipedia emerged top of the results table. Almost every non-news search I made came up Wiki – except interestingly, Celtic Football Club, where the club's own site is top. But even here Wikipedia was third.

This website is well on the way to becoming the number one source of information for the entire world. Wikipedia is a valuable resource, and is greatly increasing the accessibility of human knowledge. However, I'm beginning to wonder if it isn't gaining a virtual monopoly on online wisdom. Which is more than a little worrying. There was a time a few years ago when Wikipedia was the butt of stand-ups and satirists because of the unreliability of some of its biographical entries, which were often full of lurid inaccuracies. These are all in the "Wikipedia inaccuracies" page on, er, Wikipedia. But no-one is laughing now. Every school and university student in the industrialised world goes first to Wikipedia when they're looking for information for an essay. Not for nothing did the Wikipedia boss, Jimmy Wales, say on the eve of yesterday's blackout: "Get your homework done early kids."

Any journalist who says he or she doesn't use Wikipedia at some time or other is lying. You can't help using it because it is always there, sitting in poll position, on every internet search. Of course, I would never use it as a source on anything remotely controversial such as climate change, or immigration, or the banking crisis. But as a means of checking routine facts – like the Conservative majority in the 1951 General Election – Wikipedia has become remarkably and conveniently reliable. This is because, with its 40,000 editors monitoring millions of corrections by users, it is almost impossible for a simple factual inaccuracy to remain uncorrected for very long. Its entries are often sketchy and tendentious, but everyone turns to them, and they mostly get the basics right.

But just consider what immense power this places in the hands of Jimmy Wales, the internet entrepreneur who set it up only 10 years ago. Wikipedia's act of self-censorship yesterday was in protest at what many in the wired community believe is an attempt by big corporations in America to kill the internet by forcing it to obey draconian copyright laws. The Stop Online Piracy Act (SOPA) and its sister legislation, the Protection of Intellectual Property Act (PIPA), currently before the US Congress, have been backed by media moguls such as Rupert Murdoch of NewsCorp. But in taking itself down yesterday in protest, Wikipedia was engaged in its own form of powerplay. Clearly on this one issue, Wikipedia is taking sides, and is denying access to information in an attempt to strong arm a democratically elected legislature.

Now, I don't hold any brief for SOPA or PIPA, which make it illegal for any website to distribute, knowingly, material that is in breach of copyright. It is targeting those file-sharing sites that our kids use all the time to share music and videos. Critics like Mr Wales claim that just by inadvertently linking to a pirate site, a website might be prosecuted under SOPA. This will drive many out of business, and curb freedom of speech. No-one likes censorship, and everyone loves free stuff – but I can understand the purpose behind the legislation, which is to halt the losses that are incurred by publishers, authors, musicians and film-makers when their work is illegally distributed through internet pirate sites.

The music industry and the newspaper industry have been brought to their knees by the internet. Bands can no longer expect to earn much from sales of their recorded music because it is offered online for nothing. Surely this is wrong? Creative people need to eat, like everyone else, and these sites are stealing their lunch.

To internet business people this sounds like special pleading from old-tech industries which have failed to move with the times. There is a "democracy of knowledge" on the web, we are told, and that it is evil to attempt to control this or to make money out of it. Everything should be free and accessible to all, in the digital republic. But how can film studios continue to invest hundreds of millions on making films if they are given away for nothing? How can newspapers survive if they have no revenue?

Moreover, web organisations aren't exactly averse to making a lot of money out of other people's work. Essentially what happens is that the revenue that may once have gone into the box office or the record store now goes to the mega websites through their targeted ads. Google and YouTube make billions of dollars through advertising around content that they haven't made. At the other end of the food chain, TVShack, the site set up by British student Richard O'Dwyer, who is being extradited to the US to face trial for piracy, was earning £15,000 a month from advertising. Heavy handed justice perhaps – but this is surely theft?

Of course it would be worrying if websites were closed down because they inadvertently link to pirated content, though defenders of the legislation insist that intent has to be proved first. Barack Obama, under pressure from Silicon Valley, has called in SOPA until it can be reviewed for any unintended threat to freedom of speech. But I can't see why copyright law should not apply on the internet just as everywhere else. The truth is that websites are just like any other publishing business and the sooner the law recognises this the better. The world wide web is not the wild west – it cannot remain unregulated. And I am really rather worried that Mr Wales has chosen to use his own muscle in trying to challenge laws which are, whatever you think of them, the product of a democratic process.

Maybe it's time to say that Wikipedia has got too big for its own good. Mr Wales's website may be on the side of the angels, but after yesterday's blackout it has lost its innocence.