The National Archives (UK) has released Guidance on Cloud Storage and Digital Preservation: How Cloud Storage Can Address the Needs of Public Archives in the UK.
Here's an excerpt:
This Guidance is focussed on the cloud and its potential role in archival storage. It aims to help public archives in the UK develop an understanding of cloud storage and its potential contribution to their digital preservation activities, and to provide a balanced overview allowing archives to understand potential benefits and risks involved and the range of options available (including not using cloud if it does not meet your requirements).
Whilst primarily targeted at public archives, the aim is to provide information that will be useful within a range of organisational contexts, and overarching advice that can be translated into the private sector where relevant.
See also the case studies.