Apple and Google were once seen as best friends in their fight against mutual enemy Microsoft, but as Google has ventured into Apple’s turf with the Chrome OS and Android smartphone OS, their BFF status has been in jeopardy. Google CEO Eric Schmidt resigned from Apple’s board of directors, citing a conflict of interest, and Google Latitude and Google Maps Navigation have been released for Android but not iPhone. Meanwhile, Microsoft’s Bing search engine is now available for iPhone.

PC World’s David Coursey writes: “On the basis that ‘my enemy's enemy is my friend,’ Apple and Microsoft could find that competing with Google requires both their efforts, with Microsoft able to provide web applications that Apple doesn't want to build. (Or does it, since Apple has been making some moves on the mapping front?)” That last comment refers to an Apple job opening that notes: “We want to take Maps to the next level, rethink how users use Maps and change the way people find things.”

While Apple and Microsoft continue to fight head-to-head in the computer market, with Microsoft CEO Steve Ballmer calling Apple’s market share gains a “rounding error” and Apple continuing to sell more Macs than it ever has, it’s possible the two could ally on the smartphone front. Or maybe not, says eWeek’s Clint Boulton, who writes in a piece titled "Apple, Microsoft to Unite vs. Google When Hell Freezes Over": “With Windows Mobile sinking and Bing a meager 10% factor in search, I'm not sure Apple would be inclined to throw any lifelines to Microsoft, which needs the help.”

He continues: “Apple frankly doesn't need Microsoft's help. Apple lives to serve the consumer and if consumers want Google applications, Apple will give them to them, or at least let them use them on the iPhone, Macs or the mythical unicorn that is the Apple Tablet. Apple would be foolish to shut out Google entirely … Talk to me in a couple years if Google netbooks are kicking butt and taking share versus Apple and Microsoft, but for now it's an iPhone vs. Android battle.”

The technology world is full of examples where companies compete but still look for ways to serve each other’s customers. See Microsoft’s Macintosh Business Unit and Apple’s Windows compatibility for iPhone, iPod, Safari, QuickTime, and iTunes for obvious examples of that. What 2010 holds is anyone’s guess. Tell us what you think in the comments section.