As anyone who has worked on a cross-functional team with no clear owner knows, “shared” or “joint” responsibility often means that everyone assumes that someone else is taking care of the problem. Without clear effort to make sure that nothing falls between the two (or more) teams, something always gets missed.
The shared responsibility model and cloud service providers
The cloud services “shared responsibility” model goes something like this: the cloud provider protects everything below a certain level (that level generally being their software) and is responsible for securing it. Consider that the foundation of your house. You, the customer, are responsible for protecting everything above the foundation—securing the house, if you will.