Ballmer talked about all of the support that its partners and OEMs provide for Windows 8. "We believe in the strength of that ecosystem and those partnerships are essential to the re-imagination of Windows," he said, alluding to Windows 8. In his tribute, Ballmer named every major chip company and OEM partner he could think of. He also said about Windows 8: "We didn't want to leave any scene uncovered."

When I asked one Microsoft executive how its hardware partners responded to the news that their software daddy was about to become a competitor, he just reiterated that Microsoft values its partners. A Dell spokesman provided this response: "Microsoft is an important partner to Dell and we look forward to introducing a full complement of Windows 8 solutions later this year." A Lenovo spokeswoman provided a similar response: "Microsoft has been and will continue to be one of Lenovo's most valued partners." She went on to tout Lenovo's tablet growth worldwide. An Asus spokesman said the company is not commenting on Microsoft's announcement; an HP spokeswoman said the same.

In other words, nobody's talking. There are too many interdependencies.

Leaving me, of course, to speculate on Microsoft's motivations. I can think of five:

1. Microsoft is dissatisfied with the progress partners are making on the tablet front. Its OEMs may be dissatisfied with Microsoft, which has dictated a minimum and vanilla set of standards for Windows Phone 7. Perhaps the same is true for Windows 8 devices.

2. Microsoft wants to push its ecosystem harder, instilling a little fear. Ballmer talked about Microsoft's bet on software, saying that the company's "unique view of what software could do would require us to push hardware, sometimes in ways that even the makers of the hardware themselves had yet to envision." The usually plain-speaking CEO put a rather eloquent finishing touch on that thought: "That's the nature of the dynamic between hardware and software, pushing each other and pulling each other forward."

3. Microsoft has Apple and Google (with Motorola) envy. Somebody has to take RIM's enterprise market share, and Microsoft has the experience and customer relationships to do it, setting up the consummate battle between these three behemoths. Today, Apple dominates in tablets, Google in smartphones, and Microsoft in PCs. Each aims to change that.

4. Microsoft indeed has some transformational changes in store. Ballmer noted that the company, with Windows 8, had re-imagined Windows "from the chipset to the user experience…to enable new capabilities and scenarios." Perhaps all of these software experiences--SharePoint and Office (in the cloud, too) and Lync and Skype--start to work better (differently even) across Windows 8 platforms when Microsoft has more control.

5. Microsoft is bored. Why else would the company hold an event in the middle of Hollywood, squeezed in between Apple's World Wide Developer Conference and Google I/O? Maybe, amid slowing growth, Microsoft is looking for the next growth frontier: optimized hardware. There are already rumors about more announcements around Xbox and Nook integration into Windows tablets, about subscription services, about phone hardware (or a Nokia acquisition), about subsidies via carriers in order to garner market share.

Somebody at Microsoft whispered that it's going to be a busy summer at Microsoft. Maybe it always is, or maybe the company has even more up its sleeve. I wouldn't be surprised.

Ballmer said Windows 8 and the Surface tablet is for the world we know. But what about the world we don't yet know?

At this year's InformationWeek 500 Conference C-level execs will gather to discuss how they're rewriting the old IT rulebook and accelerating business execution. At the St. Regis Monarch Beach, Dana Point, Calif., Sept. 9-11.