A symbolic moment, this: in Q4 2013 the number of computers* sold by Apple was larger than the number of Windows PC sold globally. If you add Windows Phone to the mix they're more or less exactly equal.
This is a pretty good illustration of the scale of mobile: Apple limits itself only to the high end of the mobile market but still sells more units than the whole PC industry.
(*Macs, iPhones, iPod Touches and iPads)
For even great clarity, this shows just Windows PCs and iOS devices - Microsoft's old business and Apple's new one. Obviously, Apple's business is more seasonal and the iOS number will probably be lower next quarter - hence my opening line: a symbolic moment.
The comments to this post were passionate but not all that productive. It's a pretty simply point: mobile is the next computing platform and it's a lot bigger than PCs in unit sales, so even the smaller player can overtake the total PC business. It really didn't occur to me that anyone would disagree with this. I've closed comments.