Whereas is a platform-as-a-service cloud, giving developers the tools they need to build and deploy Web applications, Amazon EC2 is primarily an infrastructure-as-a-service cloud, offering on-demand access to customizable virtual machine instances.

Azure simplifies the building of web applications in a way that Amazon does not, but Amazon's cloud-based virtual machines have the benefit of working with multiple programming models, O'Brien says, predicting that over time Microsoft will move more into infrastructure-as-a-service and Amazon will cross over into platform-as-a-service (PaaS).

O'Brien, senior director of Microsoft's Platform Strategy Group, discussed his take on the cloud market in an interview with Network World, as well as a public presentation at the recent , hosted by IDC and IDG Enterprise. 

"It's a double edged sword," O'Brien said in the interview. "The reason people like infrastructure-as-a-service is because it's programming model agnostic. The bare metal VM doesn't care what language you wrote the application in, it doesn't matter what tools you use and what runtimes you've targeted. If it runs on Windows or Linux, give it a virtual machine and it will run just fine. The problem is it's a lot of extra work. You're responsible for that virtual machine the same way you're responsible for a server sitting under your desk. You're responsible for turning it on. You're responsible for turning it off. You're responsible for applying a patch or an update. If Red Hat applies a Linux patch, and you have a Linux VM running on Amazon, you have to apply that patch yourself. They won't do that for you."