They are left out for being PaaS (Platform as a Service) rather than IaaS (Infrastructure as a Service). Guy’s methodology is outlined in the first post in the series at: http://www.jackofallclouds.com/2009/07/top-sites-on-amazon-ec2-july-2009/ and August of 2009 was the first time he listed out multiple providers: http://www.jackofallclouds.com/2009/08/state-of-the-cloud-august-2009/

I assume that Windows Azure and Google App Engine are missing from the preceding graphs because they aren’t commonly used to power Web sites.

Is this assumption correct?

Thanks in advance,

–rj