That's just silly given how much of Amazon's documentation strongly encourages you to use multiple AZs and regions for reliability. I've included a sampling of their whitepapers below; this is also what their salespeople tell you and what you have to click past any time you provision an RDS instance, ELB, etc.

http://media.amazonwebservices.com/AWS_Cloud_Best_Practices....

“Be a pessimist when designing architectures in the cloud”

http://media.amazonwebservices.com/AWS_Web_Hosting_Best_Prac... “As the AWS web hosting architecture diagram in this paper shows, we recommend that you deploy EC2 hosts across multiple Availability Zones to make your web application more fault-tolerant.”

http://media.amazonwebservices.com/AWS_Operational_Checklist...

“We have deployed critical components of our applications across multiple availability zones, are appropriately replicating data between zones, and have tested how failure within these components affects application availability”