Cringely :

Remember when Ballmer talked through his hat a few years ago about how Microsoft was headed to a model of Windows based primarily on ad revenue? There’s no way in Hell that business model can be sustained for Windows or the PC (or for Macs, either). But make the platform cost $199 and be replaced every 24 months, build-in mobile subscription revenue, MobileMe subscription revenue, content revenue, app revenue and ad revenue, with none of those involving much effort or expense on Apple’s part at all and the future becomes clear.