Cloud computing has become a critical part of many systems from all sorts of viewpoints. Risk and security has been a major concern, and it is gradually being addressed. The question of auditing cloud systems is being addressed in some quarters, but is way behind what is needed.
A new standards organization - cloudaudit.org - supported by some 250 organizations involved in the cloud, has begun to establish standards for cloud audits. While the standards so far are far from completed, there is now enough to work with, and some organizations have begun to do so. Here is an overview article on cloudaudit.