Professional journalists in the age of the internet look as doomed as blacksmiths in the age the combustion engine. Local newspapers are disappearing. National newspapers and commercial TV stations are seeing the web take their advertisers.

Even the gloomiest forecasters expect there will still be a few reporters around in 2025, but as with blacksmiths, we will be curiosities.

There is no point arguing against the inevitable and many optimists believe that the destruction of the old order should be welcomed. In Here Comes Everybody, Clay Shirky celebrates the switch to a democratic world where publishing costs next to nothing and anyone with access to a computer can write for an audience which in theory extends to everyone with a computer on the planet.

He quotes the example of Alisara Chirapongse, a marvellous Thai student who blogged mainly about fashion. Her readership was tiny, until the 2006 Thai military coup. Chirapongse ignored a news blackout and described life in Bangkok. She posted photos of mutinous troops on her website and organised a campaign against the army's attempts at censorship. When the crisis was over, international admirers left and she went back to sharing thoughts with her friends.

Newspaper correspondents in Thailand may have been censored by the military. If their editors had sent them in from London, they may not have known the language or understood Thai politics. It is possible that Alisara's writing was not only equal to the work of her professional rivals but superior and more widely read.

Why, then, mourn the passing of the hack? The best reason for wanting my colleagues to survive is that serious reporters and broadcasters offer a guarantee that what they say is true. If they stray, their editors impose journalistic standards and insist on objectivity. They may not have the best or fullest story or the most vivid account, but readers should be able to assume their work is reliable, while a blogger's commitment to objectivity can never be assumed.

The BBC offers the most comprehensive guarantee. Politicians and lobbyists want to influence it more than any other news organisation because, despite occasional lapses, its reporters have earned the right to be believed.

The corporation should be becoming the most important news institution not merely in Britain but the world. The technological changes that are wrecking the profitability of newspapers and commercial TV in all advanced countries mean that many will think hard before sending a reporter to cover the next coup in Thailand. The BBC, whose £3bn income is guaranteed by the state, should have no comparable worries.

Yet far from looking like confident men and women ready to fill the gaps left by their retreating competitors, BBC journalists are a harried and miserable bunch.

This week, they will strike over a threat to jobs in Asian branches of the World Service. Despite the obscurity of the cause, union members voted 77% in favour of action because they fear that they will be next.

To use old-fashioned language, they are caught in a class war. Wealthy managers, 50 of whom earn more than the prime minister, have turned on their less fortunate subordinates. After Jonathan Ross's obscene phone calls, the management made reporters go on childish courses to teach them how to be good boys and girls, even though the scandal had nothing to do with them.

At the March meeting of the BBC Trust, Mark Thompson, the director-general, described how he had cut 7,200 jobs since 2005 and was planning to cut another 1,200. South America, West Africa and much of Europe are barely covered, while the best British programmes are downsized. Managers have reduced the number of journalists working for Radio 4's Today from 17 to seven. After imposing years of cost squeezes, they are insisting that Newsnight accept a further 12.5% reduction in its budget.

At the morning conference on what the news agenda of the day should be, editors don't always listen to their reporters but run after stories from the Mail, Guardian and Telegraph. Every newspaper editor I know is trying to think of ways to maintain reporting standards, but they fear they are fighting a losing battle. The BBC is not thinking about how it will cope if one day the Mail, Guardian and Telegraph don't have any stories.

The net is partly to blame for the downgrading of journalism, but not, for once, because it is destroying a news organisation's business model. The BBC has willingly poured hundreds of millions into developing its online sites and iPlayer, while getting as far away as possible from the democratic hopes of Shirky. He justifies his enthusiasm by describing the writers and networkers who have used technology to campaign against abuses of power. In other words, he cares about content as much as process. The BBC is so uninterested in content that it is sacking its content providers or journalists as we used to call them.

The paradox of the BBC's strategy is that the more it spends on expanding into cyberspace the less it has to say.

Once, the disputes within the corporation would have been a local affair. Now, as traditional media contract, they are of national and maybe international importance. No rival can fill the gaps if the BBC pulls back from comprehensive reliable reporting. Soon, if its camera crews do not go to Nigeria, no one else's will.

All over the world, there are Alisara Chirapongses providing breadth and depth, which we never experienced in the 20th century. They find it harder to provide a solid record of events, which others can refer to and move on from. Critics of the BBC say that it is using the power of its protected status to take audiences from its rivals and there's some truth in that. They should be as worried about the type of BBC its managers are creating and how patchy and thin its news coverage is becoming.

In this time of upheaval, the BBC has a public duty to invest and broadcast the journalism that others cannot afford. It is failing spectacularly to live up to its responsibilities.

• Nick Cohen's essays, Waiting for the Etonians, are out now from 4th Estate