Microsoft didn't have to lose data center virtualization to VMware. It wasn't a question of inferior technology or product functionality. They lost because their business model was wrong.
Microsoft's Server and Tool Business (STB) has done extremely well by identifying markets where complex software functionality can be engineered for simple installation and use, and then brought to market at a disruptively low price point. Time after time this model worked: Windows Server, Systems Center, Exchange and SharePoint. Not surprisingly, when it came to virtualization, this was the business model: offer lots of functionality at a disruptively low-price. Why did it fail so badly in this case?
It failed because virtualization was different. Virtualizing a set of servers isn't like upgrading the operating system or Office. Virtualization enables significantly improved economics but along the way it requires significant changes in how the data center infrastructure is managed and how the data center is organized. Therefore it isn't surprising that customers didn't just jump into virtualization. Instead they brought in consultants to help them plan and implement, and along the way created a new channel focused on the delivery of virtualization solutions.
VMware had an "expensive" solution (although still a very smart investment considered by itself). Selling the VMware solution made a lot more sense for the channel because they made a lot more money doing it, and at beginning the VMware solution was domonstrably "better" than the Microsoft solution (more advanced functionality). So if a channel partner could make a lot more money selling VMware guess what they did?
As the Hyper-V solution caught up (and with System Center in many ways surpassed VMware) guess what happened? More or less nothing, because the channel had no incentive to switch brands. Yes, VMware has an "expensive" solution, and customers would like a "cheaper" solution, but that's not enough given the partner economics.
I finally understand what people were trying to say when they noted that Paul Maritz knew the Microsoft play book ("he had written it"). The genius wasn't just to understand your big competitor well; it was to jujitsu Microsoft (use their own weight against them). The bigger question is why Microsoft didn't see it coming. The ultimate loss is enormous. Windows Server has done extremely well in the data center. System Center is remarkable management system. But now flanked by VMware on both sides it's going to be challenging to get out of the pincer. Ballmer has changed the STB management. Microsoft is a smart and powerful company. Next move is necessarily theirs.
Paul Maritz must have had a reasonable idea of what he was getting into. In most aspects VMWorld was been a smashing success -- large and enthusiastic crowds, a big ecosystem pavilion. Paul did an excellent job on the keynote considering he had been on the job for all of 10 weeks (he was blessed by the fact that Diane Green was truly an awful public speaker so the hurdle was low) that dovetailed nicely with CTO Steve Herrod's excellent technical keynote the next day. Maritz sounded more like the leader of a $2B software company than VMware. The plans sound like business plans: (1) Paul admits they are really a platform vendor and they talk about a Data Center OS, (2) he put a stake in the ground that the Cloud was going to be a real business and (3) that they were getting serious about VDI (now branded as vClient). All of this makes sense if you're trying to answer the question "How will VMware make money?" (the question that Diane never wanted to talk about it). On the other hand, with the collapse of the "virtualization" reality distortion field came a further (and I'm sure painful) deflation of the stock, taking it down well under the initial IPO price. Some of the commentators apparently never realized that VMware really does compete with the big boys. Oh well...