But there’s a new battle front to watch, now: Facebook, which continues to grow like crazy, is quickly becoming a threat to everyone.
These three companies are the new titans of Silicon Valley, and watching them duke it out is going to be the greatest show in tech for years to come.
Apple and Google probably spend more time thinking about each other — and now Facebook — than they think about long-time foe Microsoft, which is in decline.
The latest moves from all the companies revolve around social networking and mobile technology.
Facebook is working on mobile phone software that could potentially threaten Apple and Google. (Though if Facebook is using Google’s Android as the basis for its software, it could also theoretically benefit Google.)
Facebook, like any tech leader, sees mobile as a HUGE potential growth area. More than 150 million Facebook users already access the service via mobile, but Facebook wants to be more than just an app. Like it's a platform on the web, Facebook wants to be a platform in mobile. So it's looking at ways to do that, including potentially tweaking Google Android to be much more social- and Facebook-centric.
Meanwhile, in the last year, Google's Android operating system has taken the smartphone industry by storm, passing Apple in market share. (Though the new iPhone 4 is still arguably the best phone on the market).
But Google's attempt to disrupt the mobile industry by selling phones directly to consumers -- the Nexus One store -- was a huge flop.
Google and Facebook are especially competitive in recruiting the best software engineering talent in the Valley, especially in light of Apple's previous 'no poaching' pact with Google. This is extremely important because if these companies can't continue to hire the best possible engineers, they're toast. (Facebook has notably hired a lot of ex-Googlers. But now people are increasingly leaving Facebook, too.)
Recently, all three companies have been making a lot of 'acq-hires,' where they buy a company to acquire its human resources. Apple recently bought LaLa, for example, Facebook bought Hot Potato, and Google does a few deals per month.
Facebook is obviously the world leader in social networking, approaching 600 million users. But Apple and Google are getting into the game.
Apple recently announced two social networks, 'Ping' for its iTunes store, and 'Game centre' for social gaming on the iPhone.
Apple has been a Facebook partner for years, so it's significant that Apple launched Ping without Facebook's help. It suggests that Apple wants to grow Ping into a significant service of its own, which could compete with Facebook.
Meanwhile, Google is supposedly hard at work on its umpteenth social networking service, 'Google Me.' Earlier this year it launched 'Google Buzz' as an add-on to Gmail, which hasn't taken the world by storm. But with daily access to people via Gmail and Google search, and Facebook looking ever-threatening, it's in a good position to keep trying.
Google is the search leader by far, but it is vulnerable.
Facebook could potentially do things in social search that Google could only dream about.
And Apple is doing interesting things in mobile search. Its App Store is already getting in Google's way on the iPhone.
And because mobile search is going to work a lot differently than desktop search, Apple could continue to hack away at Google's dominance on mobile devices. Earlier this year, it bought a company called Siri, which puts it squarely into the mobile search business.
Apple recently boasted that it has more than 160 million iTunes accounts with credit cards, to which it can sell apps, music, and other entertainment. It's also cranking up its written media business with iBooks and a forthcoming digital newsstand. And iTunes payments also power a thriving virtual goods business for iPhone games.
Facebook, meanwhile, is trying to turn its payments platform into a real business, supporting huge Facebook games like Zynga's FarmVille. This could play a big role in its mobile business. And Facebook's identity platform -- sign in with Facebook, also known as 'Facebook Connect' -- is massive.
And Google has been trying to make Google Checkout into something big for years, with some success. Android's further adoption could be big for Google's payment plans.
Apple and Google both have functional, growing mobile ad businesses, both are likely eyeing TV ads, and Google, of course, has its mammoth search ad business. And Facebook's social ad platform is taking off, expected to generate more than $1 billion in revenue this year.
In mobile, they're taking slightly different approaches -- Apple more closed, Google more open -- but they both seem to be doing fine for now. Mobile advertising is such a tiny market that there isn't much to talk about yet. And that's why it's OK that Facebook has put zero effort into making any money on mobile devices. There are no ads on any of its mobile products. Someday that will change. We anticipate Facebook will eventually want to enter mobile advertising, with a social slant. But for now, it's still beyond the horizon.
Facebook's platform isn't an operating system the way Apple's OS X or Google's Chrome OS are, but it's quite the platform. Many of Facebook's apps have tens of millions of users, who access those apps via Facebook. This is the platform that Facebook wants to extend to mobile.
Meanwhile, Apple uses OS X for the basis for its Mac computers, iPhone, iPad, iPod touch, and likely the new Apple TV.
And now Google is moving to directly compete with OS X via Chrome OS, a lightweight operating system for Web-focused computers, and Android, which will power tablets and Google TV.
Facebook hasn't showed up in the 'office' apps race, except as a partner to Microsoft's Docs.com. This is probably all it will do for a while. But Docs make sense for Facebook, especially for its younger, web-savvy user base that thinks of Facebook as an operating system.
Meanwhile, Google Docs, Google's Web-based office apps suite, is mostly designed to disrupt Microsoft's Office cash cow. But Apple has one of those Office rivals, too: iWork, its suite of word processing, spreadsheet, and presentation software, which is especially popular on the iPad.
Facebook, at least at one point, had plans to turn its messaging platform into a 'Gmail-killer' email service. But for now, that hasn't happened yet.
Meanwhile, For $100 a year, Apple's MobileMe offers email, photo and Web hosting space, calendar syncing, and more. Google's Gmail, Google Calendar, Picasa, and other free products offer most of the same features for free.