Game-Changer for Microsoft

Desperate for growth as its core business ages, Microsoft hasn't been able to make inroads into the burgeoning online advertising market. In March, investment bank UBS estimated Microsoft's share of global online ad revenue to be only 7%, compared with 43% for Google and 23% for Yahoo!.

Microsoft also continues to lag behind Google and Yahoo! in search engine market share, with just 10.9% market share in March, as compared with 48.3% for Google and 28.5% for Yahoo!.

That continued flailing is likely silencing those inside the company who believe Microsoft can build -- rather than buy -- its way into nearly any market, given its vast engineering resources.

Meanwhile, Google's acquisition of DoubleClick extends its reach beyond the search ad market, where it has dominated, into display advertising. But more importantly, the company will find ways to sell display and search ads in tandem, enabling buyers to manage their campaigns through one system, as Google CEO Eric Schmidt took pains to point out in a conference call to investors announcing the DoubleClick deal.

The move will allow Google to increase its stranglehold on the online ad market, making it even more difficult for Microsoft to make inroads.

Google is also working to invade several other ad media, ranging from print to video, radio and mobile, simultaneously. The company's goal is to create an operating system for advertising, Schmidt has recently said. And if there's one company that understands how difficult it is to displace a dominant operating system, it's Microsoft. Its own Windows operating system for PCs has allowed it to be the dominant technology player for decades.