Application Security within the Virtual and Cloud Environments

Virtualization and Cloud Security architects, pundits, and writers like myself often talk about protecting the data within the virtual and cloud environments. However, in order to protect that data we need to be able to determine how the data will be used, accessed, modified, and eventually removed. So, how can we understand data security without understanding the application around it. But there is an even more fundamental problem, how do we define the application and the security measures we should take?