Read the full article at ABC.

Of the 20 million Australians who use the internet, the vast majority of us also use Facebook — with over 16 million Australian accounts.

Around the world, the social media platform has almost 2 billion users — more than a quarter of everybody on the planet, and that includes those either too young to go online, or too poor to have access.

At the same time, more and more of us are spending more and more time on Facebook — 1.7 hours a day, on average.

Facebook has turned that into a business earning more than $US16 for every user around the world.

That turned into a staggering profit of more than $US10 billion last year — 177 per cent more than 2015.

"They are arguably the most successful company in human history at just gathering people's time and turning that time into money," New York Times journalist John Herrman told Four Corners.

In 2014, Facebook researchers published the results of a study, in which they deliberately skewed the "mood" of the news feeds of almost 700,000 users.

They tweaked the algorithms to give some users predominantly negative posts, and others generally more positive news to see just how much they could influence people. They then monitored users' posts to see if their moods shifted.

The company later apologised for the study, admitting its researchers had crossed a line, but the results were still revealing: they confirmed the more negative our news feeds, the worse we tend to feel; and the more positive, the happier we become.

The shift was quite small for each user but statistically significant overall, proving the social media platform is so deeply embedded in our lives that it has an impact not just on what we see of the world, but also how we feel about it.

Psychology Professor Ethan Kross from the University of Michigan said these networks were "now a part of our life".

"What makes them so interesting is how quickly they've transformed the way human beings operate, how we interact with one another and so the real challenge is to understand how to navigate the networks optimally."