
1. First And Foremost: SoftwareAt Microsoft, Steve Ballmer spends the vast majority of his time thinking about software. He knows the ins and outs of operating systems, office productivity solutions, and the cloud. But does he know that much about hardware? At Apple, that would be his focus. And he might not be up to that task.

2. It’s A Respect ThingIf Ballmer would ever be put in charge of Apple how would he gain the respect of his employees? For years, Apple and Steve Jobs have criticized Ballmer for not knowing how to adapt to the changing times. If Ballmer ever took over Apple, he would join a company that’s full of people who would have no faith in his leadership. That’s not a good thing.

3. Innovation Reigns SupremeAt Apple, innovation means everything. The company continues to push the boundaries and try new ideas. And while Microsoft has been somewhat innovative in the past, for the most part, the company’s focus has been on maintaining its grip on consumer and enterprise productivity. And it has done that with evolutionary updates to its popular platforms. To change gears like that would be exceedingly difficult for Ballmer.

4. Investors Would BailWhenever a new CEO takes over at a company, there is always some discontent among investors who worry that the future won’t be so great. But if Ballmer took over Apple, one can bet that the Cupertino, Calif.-based company’s shares would plummet. Steve Ballmer is much different than Steve Jobs, and so far, investors have proven their faith in, and loyalty towards, Jobs. With Ballmer, all that might go away.

5. Would Mac OS X Be Opened Up to Vendors?One of the central tenets of Microsoft’s strategy over the years has been offering its operating system to PC vendors. At Apple, the company controls both software and hardware, and doesn’t license its operating system. Would that change under Ballmer? It’s tough to say. But if so, it might not be long before Apple is in trouble again. As Steve Jobs has said in the past, maintaining its grip on Mac OS X is integral to Apple’s Mac success.

6. How About the iOS?If Steve Ballmer opens up Mac OS X to PC vendors, it likely wouldn’t take long for him to offer iOS to smartphone makers, as well. After all, iOS is a highly sought-after operating system, and in the short-term especially, Apple could make boatloads of cash off of it by licensing it to other companies. Whether or not that would be a good idea for Apple would be up for debate, but it’s highly likely that Ballmer would like it.

7. Apple Cares Most About ConsumersOver the years, Microsoft has been able to cater to both consumers and enterprise users. But if the company was forced to rank which market mattered most, it would undoubtedly tap the enterprise. That said, it would be a much different story at Apple, since the iPhone maker cares most about consumers. That alone is a major shift that Ballmer would need to overcome.

8. It’s A Different Corporate PhilosophyOne of the biggest issues for Ballmer if he were to go to Apple, would be the differences in the corporate philosophies of the two firms. Apple is a secretive, forward-thinking company with a “premium” focus. Microsoft is more practical, and willing to show off future products months, if not years, in advance. Innovation isn’t as important as profitability at Microsoft. Those two corporate cultures are enough to make Ballmer seem lost at Apple.

9. Think About the Mobile HardwareOne of the biggest issues for Ballmer if he were to take over at Apple would be making decisions on the next versions of the iPhone and iPad. Apple CEO Steve Jobs has played an integral role in the development of all Apple devices, including — and especially — the iPhone and iPad. Ballmer lacks the eye for design that Jobs has, and if decisions were left to him, there’s no telling what would become of Apple’s mobile division.

10. He’s Not Too Fond of AppleAlthough there are several reasons Ballmer could never succeed as the CEO of Apple, the simplest is that he doesn’t necessarily like Apple. Over the years, he has complained about the company, scoffed at its ideas, and generally shown contempt for how it operates. Unless Ballmer could find a way to put all that aside, it’s unclear how he would even be able to join Apple, let alone run it.