Just got done reading this article on how Apple is going down the wrong path with their "closed" systems.
As I like to say, I'm a PC-and-a-Mac. I have nothing for-or-against Apple or Microsoft. I love iPods, hate iTunes Music Store (but love iTunes for managing my music library, love iPhone, hate Windows Mobile, love Xbox and Xbox Live, am indifferent to my iMac and indifferent to my Windows laptop. And I love Amazon MP3 :)
I heard this "open system" line five years ago as iPods really took off. Apple hasn't lost it's leadership position yet. Instead, they continue to innovate, deliver value to customers, and reap the profits. They have a solid business model (deliver a seamless end-user experience software to sell music as a loss-lead to sell devices at a huge profit).
Did the Wintel decoupling of hardware and software enable Wintel to beat Apple in the 80s? Maybe. Maybe not. I think they delivered something cheaper and easier-to-use. Was that because of the decoupling? I think so, but Apple could have played the price war with them (especially when Apple had the market share). Apple chose not to, they lost.
Here's the key point: open platform is not an end-user requirement.
Google or Microsoft will take market share from Apple when they build a better product or innovate a better model (something that beats the device-software integration currently done very well by Apple).