Call it a tale of two tech giants - whose collective shadow looms large over vast swathes of the Australian economy.
This time a year ago, Facebook and Amazon were neck and neck in terms of market value (like they were for the better part of the preceding four years).
Then a gap between the two opened up. And it has progressively widened ever since. It now stands at more than $US500 billion ($694 billion).
Amazon this week became the second trillion dollar company (in US dollars) on the planet, following Apple which reached the milestone in August.
Meanwhile, Facebook fell into bear market territory - its shares are down more than 20 per cent since late July - with myriad scandals still swirling around the social platform, and fresh signs that users are moving away from it.
Now, these two companies operate in completely different corners of tech - one is an e-commerce 'everything store', with a juggernaut cloud computing side business that has morphed into its main profit centre. The other sells ads.
As such, perhaps we shouldn't read too much into their divergent paths over the past year.
On the other hand, the relentless rise of Amazon, and Facebook's fall from grace are an illustration of how quickly and dramatically things can change in the world of big tech - a sector that now dominates the US stockmarket, and a sector many Australian investors are only just becoming accustomed to.
It's been a torrid year for Facebook, almost entirely of its own making, and reflecting its rampant growth in its early years of existence.
There was the Cambridge Analytica scandal - which saw the data of millions of users potentially harvested by a political consultancy with links to the Trump administration (resulting in regulatory investigations, including in Australia).
And there were ongoing revelations about how the platform was manipulated by Russian troll groups during the 2016 elections - a topic that was discussed at Senate hearings again this week attended by its chief operating officer Sheryl Sandberg, Twitter chief executive Jack Dorsey (and no one from Google).
Overnight, a survey of nearly 3,000 Americans conducted in May and June this year by the Pew Research Center made for grim reading for Facebook and its investors.
Among other things, the survey found that 26 per cent of users had deleted the Facebook app from their phones, and 42 per cent had taken a break from the platform for several weeks.
"It is a little concerning from the perspective of a shareholder in Facebook," acknolwedged Andrew Macken, portfolio manager at Montgomery Global Investment Management, which holds shares in the giant social network.
"That said, the resilience of this business lies in the portfolio of properties that Facebook owns - which is not just Facebook itself. The company also owns Instagram, Messenger, WhatsApp - with others on the way. Of these additional properties, only Instagram has started to be monetised."
As for Amazon, its rise has been powered by strength in its cloud computing business (in which it rents out servers and web infrastructure to big companies) and its ongoing expansion into new markets, such as Australia.
The hype of Amazon's Australian invasion may have outweighed the reality, but it is still very early days for that experiment.
However, the bigger Amazon gets, the more scrutiny it is likely to recieve from regulators. In recent months key figures from opposite ends of the US political spectrum have attacked the company.
US President Donald Trump has persistently admonished Amazon (whose CEO Jeff Bezos owns the Washington Post). Last week left-wing Democrat Senator Bernie Sanders introduced a bill (the BEZOS act) designed to shame companies like Amazon into paying higher wages.
For a quite a while, the so-called FAANG (Facebook, Apple, Amazon, Netflix, Google) grouping of big tech stocks were a one-way bet. That is certainly not the case anymore.
But as Facebook's experience over the past year shows, and to paraphrase Hemingway, in tech things change gradually, then suddenly.
