Microsoft this week published a best practices guide for writing applications to its Windows Azure cloud computing environment.
http://download.microsoft.com/download/7/3/E/73E4EE93-559F-4D0F-A6FC-7FEC5F1542D1/SecurityBestPracticesWindowsAzureApps.docx

"We wrote this paper because no matter how many defenses we add to Windows Azure, it is important that people building software or hosting services in 'The Cloud' understand that they must also build software with security in mind from the start," blogged Michael Howard, principal security program manager of Microsoft’s Security Development Lifecycle team.

Urs