Some quantitative data - we monitor Alexa and Fortune 500 marketshare for cloud services. This article is mostly accurate - Google has not taken much marketshare according to our stats. Currently, EC2 is 13% for Alexa 1k/10k and 11% Fortune 500. Rackspace is 5.5% Alexa 1k/10k and 19.4% Fortune 500. Google is under 1% for both, while Azure is between 1-2%. Our stats are available here:

http://blog.cloudharmony.com/2014/12/compute-marketshare-ale...

https://cloudharmony.com/cloudsquare#compare-aws:ec2-and-goo...

Edit: added blog link