Google’s market cap has surpassed that of Microsoft. Market gyrations continue, so for all we know it's possible for Microsoft to inch back ahead of Google tomorrow. But the milestone for Google is meaningful nonetheless.
Simply put, it means the PC isn’t as important as the web. The operating system is not nearly as important as content.

Google’s entire business is based around helping searchers find content, while helping publishers monetize their content.  Android is an extension of this, as is YouTube, despite most of the revenue coming from advertising in the form of Adwords (and Adsense). 

It’s hard to consider Microsoft much of a growth business anymore.  The PC is a mature product segment.  Windows OS is well established and represents more of a stable business than one with exciting growth. Same goes for the enterprise components of Microsoft’s business.

But the web? Still growing. Like crazy. Bing has been no match for, and Microsoft is nowhere in video (think YouTube) and scrambling to make up for perpetually failing to gain share in mobile with Windows Phone 7 and, soon, Windows Phone 8.  Meanwhile, Android has become the No. 1 mobile operating system on the planet. 

Microsoft is the established leader of the old world. That world consists of an expensive operating system running on cheap hardware. The new world consists of operating systems that come with mobile hardware, and run a variety of cheap apps and connect to cloud storage. Google and Apple are making life incredibly tough for Microsoft.

Bill Gates is unquestionably brilliant.  He is the king of the PC era. He always will be. And it’s rare for a technology company to hang onto its leadership as the market moves through a powerful transition, as the computing market did from desktop PC (and OS) to the web. Google is winning. The stock market is telling us this through buying and selling votes. 

It’s undeniable, and it’s exciting to see it finally happen.