When should one use the following: Amazon EC2, Google App Engine, Microsoft Azure and Salesforce.com?

Question

I am asking this in very general sense. Both from cloud provider and cloud consumer\'s perspective. Also the question is not for any specific kind of application (in fact the in

Answer 1

One can also take advantage of the benefits of PaaS (let's say, Google App Engine) and extend it, at times and if necessary, by pulling out some virtual machines from IaaS providers (e.g. Amazon) to do some number crunching then just send back the output to Google App Engine.

This way, you get the best of both worlds -- you can rapidly develop scalable apps in GAE, then you can always augment it by running any program you want from Amazon virtual machines.