Then Microsoft would be just another provider of virtual servers. I dont think thats a good future goal for a 300 billion dollar company.
Conversely to Gruber, I see Microsofts future in client software and hardware. Apple and Google have put computers in every pocket. But only the consumption part of it. The race for the production tablet has just started. And with the Surface Pro, Microsoft has the first product out there.
Just like Amazon they are adding their own custom services to the package which is easy to consume.
This can be storage, authentication, federation, messaging, queueing, etc.
And like Amazon they are building their own services (like AD in the cloud, Xbox Live, hosted exchange, Office 365, etc) on top of this infrastructure, so like for Amazon, the infrastructure they are selling literally comes for free.
They don't have to. They can keep on using their free and open stack, but moving to Azure instead of using Google compute engine or AWS.