But in the immediate aftermath of the event - the worst mass shooting in modern United States history - widespread confusion was apparent online.

Phony reports from a message board wrongly identifying the gunman were prominent on Google's 'Top News' page in US, and also made their way into Facebook's algorithms, The Washington Post reported.

It's troubling evidence that, despite sweeping condemnation of the two giants of the internet for their role in spreading misinformation during last year's US elections, and despite pledges by both companies to deal with the issue, "fake news" remains a serious, unsolved problem.

Google and Facebook have a collective market value north of $US1 trillion, and ample financial resources. So, are they not doing enough to deal with fake news (by which I mean intentionally false information designed to look like reputable news - not something a politician disputes or disagrees with).

Or is it impossible to put the fake news genie back in the bottle now that it's out?

Facebook earlier this year outlined a series of steps designed to curtail fake news, including pledges to employ more human fact checkers. According to at least one estimate, it might need to spend $1 billion to fully get on top of it. A sizeable sum, yet one that the markets are utterly unconcerned about at the moment, judging by the share price.

Yet Nick Enfield, a professor of linguistics at the University of Sydney, who has studied fake news as part of the university's Post Truth Initiative, doesn't think fact checking is going to cut it.

The volume of information is just too big to deal with, he reckons. It is "just too weak a solution, because the internet is an open resource," he says.

Enfield thinks information literacy should be taught more seriously in primary schools and high schools, to make readers more discerning and critical. "The only way to change the way fake news creators behave, is to change the behaviour of the audience," he says.

A full three days after the incident, it wasn't hard to find questionable, hyper-partisan content from the US related to the Vegas shooting incident on Facebook.

A quick search I did on the social network brought up a story claiming that an Australian eyewitness had indirectly revealed the "SHOCKING TRUTH" about the attack - that it was part of a vast conspiracy involving a New World Order and the corporate media.

Another post, published in August, but which seemed to have resurfaced in the wake of Las Vegas, said Australia's gun control laws were "collapsing".

(As Fairfax's Nick O'Malley reported this week, studies suggest Australia's gun laws have indeed been weakened. But this post, framed for a conservative US audience, seemed to imply the laws were not working, and are in disarray).

Should Australia be worried?

While Australia seems less prone to a fake news driven societal breakdown than the US - we are more moderate, and more trusting of government than the US - we should not be complacent.

"The really strategic fake news propagators are not targeting Australian affairs at the moment, maybe its just a matter of time," says Enfield. "But it's still affecting us."

The content farms behind the fake news phenomenon (often operating outside of the US) did attempt to meddle in France's recent elections.

Regardless, Australia is heavily influenced by the US culturally, politically and militarily, so what happens there matters to us. A lot.

Criticism of Facebook and Google by traditional media outlets (including Fairfax Media, publisher of this column) is often dismissed by the tech community as self-serving. The digital duopoly has totally outmaneuvred traditional media companies in the online ad market, decimating publishing revenues.

So, it must be acknowledged that the press also needs to play a role in combating fake news.

Another sad story this week serves to illustrate the point. When the popular singer Tom Petty was rushed to hospital, numerous outlets (including venerable publications such as Rolling Stone magazine) reported that he had passed away, even publishing obituaries, before the fact.

Beat-ups, click-bait, and misleading stories all pre-date the fake news phenomenon. The media must accept these practises played a role in eroding trust with audiences, creating a void fake news has been able to fill.

But Google and Facebook's algorithms and business models have helped amplify misinformation on an unprecedented, industrial scale. For that they must shoulder the blame.