Investigations by US authorities into the bomb attacks on the Boston marathon have relied heavily on ‘crowdsourcing’, with pleas issued to the world  for help in solving the crime.

Harnessing the power of the internet in this way is not new. But the scale of it in this case is unprecedented. And much of the resulting activity has been grossly uninformed and downright speculative.

An FBI agent asked the public to inform them of possible leads – people they’d seen near the finish with significant sized bags, anyone who they’d heard of researching how to make bombs, in short, any relevant suspicious behaviour.

This prompted websites to publish photos of individuals deemed to be acting suspiciously near the marathon’s finish – and several innocent people were smeared in the process.

It’s true, public cooperation often leads to cases being solved. But the danger here is that suspicions and speculation get exaggerated and become ‘facts’. This doesn’t help any live investigations.

Some of the websites, such as Reddit, warned speculation could wrongly single out innocent bystanders. But such warnings were mostly overlooked with individuals subjected to trial by speculation. One US newspaper even accused someone of being a suspect – on its front page.

English-born Iranian comedian Omid Djalili once joked that he’d inadvertently emptied an underground train carriage in London by rummaging for some misplaced possession in his racksack, all the time muttering at himself in Farsi.

But what’s going on is no joke. It seems a swarthy complexion and a ruck sack is all it takes to be accused of terrorism.

The frenzied online atmosphere has not been helped by some of the media channels covering the man-hunt in Boston.

As ever, the limitations of 24-hour rolling news have been clearly exposed as news anchors speculated endlessly amid a lack of clear facts.

“Not wrong for long” is no way to run an authoritative news organisation. And, given the danger of vigilantism, this mantra is one that they and the internet speculators would do well to ditch.