I am about to plan and build a large scale REST service. Because of that I have looked into how I could make my setup in the cloud. At first I wanted to do it with Amazon RDS and Amazon EC2 - however I then looked into the various PHP cloud platform services (PHPFog, cloudControl, Orchestra) which looks like exactly what I want.

However I do have some questions regarding this:

* What is the overall difference between the three services? (PHPFog, cloudControl and Orchestra)
* I want a platform that can scale automatically at peak hours, meaning that I should not have to pay for the resources needed at peak hours all day. As to what I have read, PHPFog do not support elastic scaling?
* How well does these perform? Could big services like Twitter, facebook etc. run on these platforms?
* Does these services support backups?
* Anything else I should think of when choosing one of these platforms? Or perhaps should I not choose one of these?