What is the difference between Windows Azure and Amazon Elastic Compute Cloud?
Azure is a service that allows you to upload an application – the cloud system will then run it on an arbitrary number of physical machines in order to provide reliability and capacity. This is done largely transparently to your code. Billing is done on the basis of number of requests/data transfered/etc. Amazon EC2 is a service that allows you to rent one or more virtual machines running Linux/Windows or some other operating system on a per hour basis. Any reliability and scaling to multiple machines you will have to code into your application yourself.