We often focus on the technological security issues of cloud computing.  We should also be thinking about physical security.  I've set foot in many datacenters, some of which featured impressive physical security measures (armed guards, series of entry barriers, etc).  Others have been lacking in comparison.

Too often, companies fail to do their due diligence on physical security when choosing a cloud provider.  Some questions to ask:  does your provider have 24/7 armed security (and how many guards), access control systems/procedures, number of independent power sources, fire supression systems, etc.