You could, in a sense, write the script the moment news of Jon Venables' "serious offence" leaked out. Think murder on the moors. Think Myra Hindley – and her doomed efforts to regain freedom. Think grief-ravaged parents from long ago, and communities bent on implacable justice. Think rampant press and quavering politicians, too.

But not, in fact, all the press – and no frontbench politician from any of the major parties. The racketing row over our "right to know" what one of James Bulger's 10-year-old killers had done now he was 27, and what he looks like today so we could hate him in person, was basically a case of tabloids against the rest.

"The chief enemy of British freedom at present is the British press," declared Simon Jenkins in the Guardian. He despised Jack Straw and Alan Johnson for "sating themselves" on cheap publicity. He hated the Sun, Mirror and Daily Mail in "full outrage mode". He argued that "transparency that contributes to injustice, failed rehabilitation and even greater secrecy is bad transparency".

And Sir Simon was not alone. Brian Masters in the Telegraph, Terence Blacker in the Indy and a judicious leader writer at the Times all worked the same rich seam of distaste. The ghost of Lord Longford, champion of a rehabilitated Myra, could almost be heard clapping from a passing cloud.

Yet this time another voice opened another front. Hadley Freeman at the Guardian is a fashion expert turning into a terrific columnist. And suddenly her laptop had been taken over by hundreds of Venables-related groups on Facebook, "all hysterically screaming about how he 'must be hung', 'should rot in prison 4 eva', should 'die, die, die'". These "portals into a brave new world are becoming little more than on-screen versions of the most retro pockets of the old-school media", complained Hadley. Hang on to justice, she pleaded. Don't confuse it with "vigilante vengeance".

But there is deeper confusion here. For whatever liberal commentators think about the haunting aftermath of child murder, tabloid editors have always realised what grips their readers. They have the previous day's sales figures on their desk when they decide today's lead story. And the big question has always been, chicken or egg? Was this a press telling readers what to think – or a press responding to what readers thought already?

That question begins to answer itself in a digital world. The clicks of web readers choosing tales sends signals right around online newsrooms. The BBC (under attack from Simon Jenkins for ramping up the Venables saga) can discover in a trice what turns viewers on. Those hundreds of Venables sites that horrified Hadley sprouted spontaneously, not because someone at Bun HQ issued instructions. We're on the dark side now.

Some of the most innovative and fascinating work in the online news world surrounds the "mutualisation" of interest between readers and journalists, a profound rebalancing of relationships. Once "we had the information and you didn't", said the Guardian editor, Alan Rusbridger, in an eloquent Cudlipp lecture the other day. But "that state is now in tension with a world in which many ... readers want to have the ability to make their own judgments, express their own priorities, create their own content, articulate their own views". Journalism, he said, might remain one source of authority – but not in "an inert context, one that can't be responded to and challenged".

Here's the rub, though, the Venables rub. Suppose "authority", from Jack Straw to the quality press, is getting challenged instantaneously. Suppose readers of the Bun think themselves quite as good as readers of the Times. Suppose we're not finding convenient scapegoats – press or politicians – but talking about ourselves, our communities, our own visceral instincts. Rot in prison 4 eva? Suppose I don't want to have mutual Facebook friends?

■ We ought to be nice to Facebook, too. Turn to one paragraph on page 4 of the Mail. "In an article by a criminologist on Tuesday we wrongly stated that he had conducted an experiment by posing as a 14-year-old girl on Facebook with the result that he quickly attracted sexually motivated messages. In fact he had used a quite different social networking site for this exercise. We are happy to set this record straight."

Well, happy or not, Facebook may get litigious. But there's one quick point to make. The lead headline on page 1 of Tuesday's Mail read "Facebook under fire". That story ran on to page 6, facing five-sixths of page 7 devoted to a piece entitled "I posed as a girl of 14 on Facebook. What followed will sicken you".

Or at least mildly nauseate Mail editors who expect better fact-checking from the people they employ – and may covertly regret that the Press Complaints Commission code isn't tougher about the need for due, equivalent prominence when somebody makes a debacle out of a straightforward yarn.