Amazon has been expanding outside of their core retail space (e.g. AWS, advertising, services, etc) while Facebook has been eating Google's advertising dollars for a while.
I wouldn't go as far to say that Google doesn't care about Apple/Microsoft, but in both cases Apple has presents on their platforms and still makes money on them. They are only competitors if you view Android as something Google makes money with rather than something Google uses to advertise Google's services.
All I've ever heard are horror stories about how advertising on Facebook does not work. I definitely don't see how ads on a social network can compete with ads on the largest search engine and almost every ad funded website in the world.
Weird, I know. Actually, I do have an account but only used it to write a Facebook app for a client, not for actual use on that mini-Internet (kind of like Geocities isn't it?)
Facebook advertising has been very effective and profitable for at least some clients. I think Google+ shows that Google is terrified of Facebook. I have no knowledge of how Google's advertising revenue is doing, and wouldn't be at all surprised if they still dwarfed Facebook.
On the other hand, google knows it is likely just a matter of time before Facebook gets it right, and when they do they are one of the few companies who could complete at scale with google.
[0]: http://www.emarketer.com/Article/Driven-by-Facebook-Google-M...
But people spend way more time on Facebook. It's entertainment, whereas Google is a tool. So brand advertising works better on Facebook. It's more like TV advertising.
Google definitely hates MS, as evidenced by how childish they act when it comes to Windows Phone. Apple hates Google, Microsoft hates Google, Google hates Microsoft. I'd say that's likely how it goes.
The human brain: simplifying complex issues with anthropomorphism since forever.
Kind of, but not really. Apple gives its operating system away for free, and sells hardware. Microsoft sells its operating system to OEMs and business customers. They aren't directly competing in the way that Coke and Pepsi are.
And Windows (of some version) still has >90% market share for desktop OSes, so OSX is not a credible threat to Microsoft in that space. Microsoft's biggest obstacle in the desktop OS space is Windows XP.
But Apple is more concerned these days in selling iPhones, which makes them a lot of money. And Microsoft wants in on that (disclosure: Microsoft employee, but speaking for myself).
Generally, the fanaticism in HN comments is much stronger than the sentiment of anyone actually working at these places.