We’re constantly monitoring the market for other feasible options and would definitely consider moving if an option comes up that makes more sense.

Security, uptime, reliability and privacy are critically important factors for us, so we have to run our infrastructure with very good partners, which we believe AWS is. AWS participates in the Safe Harbor program developed by the U.S. Department of Commerce and the European Union and has certified, that it adheres to the Safe Harbor Privacy Principles agreed upon by the U.S. and the European Union.

Also check this video by AWS to get a feeling for how important these aspects are for them:
http://aws.typepad.com/aws/2012/05/amazons-ciso-on-aws-security.html