What many Office 365 users don’t seem to appreciate is that Microsoft backups up their data. Not only their emails but also their SharePoint data. This is all part of the service.
Now, equally valid questions are how often do they do that and for how long is a backup retained? The answer to these questions can be found in the service descriptions for each service:
Enterprise plans - http://www.microsoft.com/en-au/download/details.aspx?id=13602
In there (under SharePoint Online Service Description, P18) you’ll find:
Data protection services are provided to prevent the loss of SharePoint Online data. Backups are performed every 12 hours and retained for 14 days.
It is always good to have multiple backups of any data source in multiple location but part of the Office 365 DOES including automatic backups of that data residing there.