Updated: AWS also has a whitepaper on Creating HIPAA-Compliant Medical Data Applications with AWS [2]. Looks like this is support on the standard non GovCloud stack.
[1] http://aws.amazon.com/about-aws/whats-new/2011/08/16/announc...
[2] http://media.amazonwebservices.com/AWS_HIPAA_Whitepaper_Fina...
Our experts advise a safe, CYA approach and mandate a BAA agreement is in place with every partner touching sensitive patient data, even if encrypted and protected on multiple levels. Thus far Amazon is not accommodating to such a request.
Other's have their own opinions and, in the end, we all weigh the risks vs rewards (including Amazon itself - I'm sure they've plenty of reasons of operating in their present gray area).
I'm not arguing that it makes sense, just that it happens.
While the compliance and security links are impressive, AWS still doesn't offer a BAA agreement for HIPAA/HITECH compliance.
There are plenty of health care companies that are held back from AWS for this single reason.
Surprisingly enough Microsoft is leading in this respect (or not, given their historical enterprise focus...) - http://www.windowsazure.com/en-us/support/security-and-compl...