BEFORE July 24, like most people you probably had not heard of Marina Joyce. Unless you are someone with a deep interest in make-up and clothes, and of the generation that has a favourite YouTuber, she likely passed you by.

Recently, the 19-year-old video blogger was at the centre of a conspiracy, thanks to helpful cybersleuths who posited a strange and improbable theory that something was very wrong over a supposed whispered “help” message in her latest video. In a few hours, hundreds of thousands of voices were contributing to the theory that she had been kidnapped by Daesh, drugged, and was being forced to make awkward fashion videos – and was attempting to lure followers to Bethnal Green, where they would be shot.

The vlogger’s fans had constructed an elaborate theory, pieced together from fragments of her online life. Bruises on her arm signalled abuse, and it was not long before her boyfriend was named and implicated and his face was doing the rounds, pegged to unfounded allegations. By the next day, there was confirmation from the police that they had visited Joyce and been assured of her safety — but it was not enough to tame the beast. By now it was national news and the scale of the conversation had gone global, with online discussions being conducted in more than 20 languages.

I know how that sounds. Any bit of news with a hashtag or a vlogger or any other digital identifier is easy to dismiss as a localised hysteria, or just run-of-the-mill online stuff. Out of context, it is almost laughable — but there is a lot going on beneath the surface of this story. Take away the particulars and you have a real-time demonstration of how conspiracies develop and the perils of citizen detective work — and the human cost of those wrong conclusions. A good intention can quickly morph into a conspiracy through the entanglement of truths, half-truths, unsubstantiated theory and outright lies. And when traditional media supports and even feeds the conspiracy, it is clear there is a serious risk of viral misinformation — and no tangible way of softening its impact.

It is not the first time the e-detectives have got it wrong and a real person has suffered. In the aftermath of the 2013 Boston marathon bombings, thanks to the sleuthing of online community Reddit, Sunil Tripathi’s name and face became synonymous with the bombings. The 22-year-old had gone missing, and the do-gooders of the internet had done the maths. Reddit had started the rumour, Anonymous released his details to the world, and even blogger Perez Hilton joined in, spreading the rumour to his six million followers. All the while, his grieving family suffered the wrath of strangers, the pain of unfounded speculation, and the horror of seeing their missing son branded a terrorist so loudly.

Except they were all wrong. Sunil was not guilty — he was dead. He had committed suicide, and his body was found floating in the Seekonk River eight days after the bombings.

Likewise, in the aftermath of Jon Venables and Robert Thompson, killers of James Bulger, being released from prison, an innocent man was caught in the crosshairs of a social-media mob. David Calvert had his photos and personal details shared online by those supposing he was Jon Venables, received serious threats to his life and had to relocate on several occasions.

In each of the instances above, however misguided, there was a desire to do good. However, that desire alone was not enough to counter the potential volatility of the internet. Once upon a time conspiracies took time to develop and spread. The internet and social media have removed that barrier, allowing theories to spring up, evolve and become glaciated by the input of a tremendous number of people in a very short space of time. The proliferation of information — be it true, false or unverified — is far beyond the realm of our control. An idea can gain visibility and the support of millions of voices, without a full complement of facts. Today, a rumour can start in the morning and be national news by noon — even if it is not accurate.

The internet has created an incubation tank for perpetual drama. We are no longer passive spectators — we can involve ourselves in the soap opera as it unfolds, fanning the flames of conspiracy and witch hunt alike, while the ability to log off divorces us from feeling like we have to take any real responsibility for the consequences.

The ability to close our computers or lock our phones stops us from seeing our targets as fully human — we can act, react and run. Few have the humility to own up and participate in aftercare once the truth of a situation surfaces.

As for Marina Joyce, she is enduring the flip-side of this drama. Since being found safe, well and very much not kidnapped by Daesh, she has faced a constant barrage of accusations and blame. She is under constant scrutiny, even from those who were leading the rescue efforts.

Even she, the real protagonist in this weird fiction, is powerless to meaningfully influence the continuing conversation.

When we spend more of our time online we could all do to remember how easily, quickly and uncontrollably the digital can spill into the real world. Even when there is a desire to do good, the shifting-sands internet discussion can change the nature of a topic instantly, and take it far beyond our own control and into the hands of a powerful collective. With this in mind, we must remember that online actions have real-world consequences — trial by Twitter can often do more harm than good.