Cloud services do occasionally fail, e.g. hardware or network failure, bugs, etc. The following URLs provide the current status for a cloud service:


Amazon Drive: https://developer.amazon.com/docs/amazon-drive/ad-status.html


Amazon S3: https://status.aws.amazon.com/


Azure: http://azure.microsoft.com/en-us/status/


Box: https://status.box.com/


Dropbox: https://status.dropbox.com/


Google Drive: https://www.google.com/appsstatus#hl=en&v=status


Google Storage: 
https://status.cloud.google.com/


Office 365: https://status.office365.com/


Rackspace: https://rackspace.service-now.com/system_status/


SugarSync: https://www.sugarsync.com/servicestatus


Review our article on Cloud Backup which considers its strengths, its weaknesses, and how Cloud services should form part of your overall backup strategy.