Amazon Drive: https://developer.amazon.com/public/apis/experience/cloud-drive/content/status
Amazon S3: http://status.aws.amazon.com/
Google Drive: http://www.google.com/appsstatus#hl=en&v=status
Google Storage: https://status.cloud.google.com/
Office 365: http://status.office365.com/
Review our article on Cloud Backup which considers its strengths, its weaknesses, and how Cloud services should form part of your overall backup strategy.